Native Hawaiian Cotton (Gossypium tomentosum Nutt.YS. G. STEPHENS2

ALTHOUGH THE WILD COTTON, Gossypium to­mentosum Nutt., is one of the more commonof the few endemic species which still surviveon the coastal plains of the Hawaiian Islands, itremains relatively unknown to the geneticist.Elsewhere it has been grown with indifferentsuccess in experimental culture. Under such di­verse conditions as those found in the WestIndies , southern Mexico, the U. S. cotton belt,and in greenhouse culture, it flowers sparinglyand even less frequently sets seeds. As a con­sequence, experimental studies have been veryrestricted, and cytogenetic analysis has been con­fined almost entirely to the few crosses whichhave been made with annual forms of therelated New World species, G. barbadense L.and G. hirsutum L. To the technical difficultiesmay be added the lack of representative collec­tions of the species in culture. The few accessionsstudied have usually been obtained from themore readily available Oahu populations, andless frequently from Molokai. These have beensupplied to cotton geneticistsrhrough the cour­tesy of resident Hawaiian botanists, J. F. Rock,O. Degener, A. Mangelsdorf, and others, andpatiently resupplied as fast as the stocks inculture expired.

As seen in culture, the different accessions 'show little morphological variation (finely to­

mentose vegetative parts, sulphur-yellow andspotless flowers, long anther filaments partlyfused in pairs, nectariless leaves, and undifferen­tiated seed fibers) . More recently, visitors to theislands, unacquainted with the taxonomy of thespecies, have sent seed samples to the mainland,and the plants grown from some of these appearto differ rather widely from earlier "authentic"accessions.

It has long been recognized that an under­standing of the degree of relationship existingbetween G. tomentosum and the other 52-

1 Contribution from Genetics Department, Univer­sity of H awaii. Manuscript received May 23, 196 3.

2 On leave of absence from Genetics Department ,North Carolina State College, Raleigh, N . C.

chromosome species of Gossypium is funda­mental for a satisfactory interpretation of theevolution of the genus as a whole. It is some­what disturbing for the cytogeneticists not toknow if the limited samples of the speciesstudied in culture are at all representative of itsnatural range of variation, nor to be confidentthat some of the "off-types" which have beencollected recently may safely be attributed to theeffects of hybridization with those 19th-20thcentury introductions of barbadense and hirsu­tum which still persist in the islands (Stephens,1963) .

In the spring semester , 1963, a temporaryappointment to the staff of the Genetics De­partment, University of Hawaii, gave me theopportunity to make a field study of the nativespecies. I should like here to record my thanksto the Uni versity of Hawaii for inviting me totheir campus and to my home institution, NorthCarolina State College, for granting me thenecessary leave of absence. Thanks are also dueto the National Science Foundation for defray­ing a major part of the travel expenses (NSFGrant G-14203) .

GEOGRAPHICAL RANGE

G. tomentosum has never been found beyondthe limits of the Hawaiian Islands. Statements tothe contrary have arisen through nomenclaturalconfusion (Watt, 1907 :69-71).3 Hillebrand'sstatement (1888 :51) that it occurred on all theHawaiian Islands probably referred only to someor all of the eight major islands of the group­Niihau, Kauai, Oahu, Molokai, Lanai, Kahoo­lawe, Maui, and Hawaii. The smaller leewardislands from Nihoa and Necker and beyond toMidway and Kure were studied by the TanagerExpedition, and the list of vascular plant collec-

3 The matter has recently been re-investi gared by Dr.R. Wilbur (Pacif. Sci. 18 ( 1) :101-103, 1964), whoconcludes that "G. sandvicense Parl. " is the correctname for the Hawaiian nati ve cotton, not "G. tomen­tosum Nutt." as used through out this article.

385

386

tions (Christopherson and Caum, 1931: 20-39 )includes only one malvaceous species, Sida fal/ax.Nor was tomentosum found on the small islandof Molokini, which lies in the channel betweenKahoolawe and Maui, by Forbes (1913a :10) .

Collections from five of the eight major is­lands are preserved in the herbarium of theBernice P. Bishop Museum . A total of 40 acces­sions includes no specimens from the other threeislands, Niihau, Kauai, and Hawaii. Niihau is aprivately owned cattle ranch, and few botanistshave had the opportunity to visit it. Mrs . Sinclair(1885:23) included a painting of tomentosumin her "Indigenous Flowers of the HawaiianIslands" which, according to St. John (1954:144-145), was probably made from living ma­terial near her home in Keikei, Niihau. The onlypublished record of tomentosum on Niihau isthat of Forbes (1913b :23).

I have be~n able to find only one definiterecord of the occurrence of this species on Kauai .This is a very old record (Wawra, 1873) whichwas kindly drawn to my attention by Dr. O.Degener. In recent years it has apparently notbeen 'Seen, though St. John (loc. cir.) listed itamong plants common to Niihau and Kauai,Ripperton and Hosaka (1942) did not recordit from Kauai, and Mr. Stephen Au and Mr.A. W. Duvel, who are familiar with the botanyof the island, inform me that they have neverseen it there. Dr. C. M. Rick recently searchedfor it among the dry western foothills in theMana-Kekaha region without success. This sug­gests that tomentosum is very rare, or possiblyextinct, on Kauai .

Concerning Hawaii, there is a rather puzzlingconflict of evidence. MacCaughey (1917:414­418) described tomentosum as one of the speciesadapted to the colonization of lava flows, withan altitudinal range of 0-2000 ft. Although hedid not state explicitly that the species occurredon Hawaii, his paper was concerned entirelywith the (geologically) recent flows which areconfined to Hawaii and East Maui. I have beenable to find no independent record of the occur­rence of tomentosum in either of these areas.Further, an altitude of 2000 ft is a considerablyhigher elevation than any recorded for theBishop Museum collections, or found during thepresent study. As will be evident later, tomento­sum is usually found as a component of Prosopis

PACIFIC SCIENCE, Vol. XVIII, October 1964

scrub, the altitudinal ranges of which have beenmapped for the Hawaiian Islands by Rippertonand Hosaka (1942 :maps 1-3) . According totheir maps there is one-and only one-regionwhere this type of vegetation ("Zone A" intheir terminology) extends to an elevation of2000 ft. This is the Kau Desert region in south­east Hawaii, and if MacCaughey 's statementsconcerning tomentosum applied to Hawaii, thiswould seem to be the only region which couldhave provided the necessary range in altitude.On the other hand, botanists who are veryfamiliar with the Hawaiian flora (Miss Marie C.Neal, Mr. L. W . Bryan, and Mrs. C. K. Went­worth) have informed me that they have neverseen the species on Hawaii, except in culture. Itwas not listed by Ripperton and Hosaka (1942)as a component of their "Zone A" vegetation onHawaii, nor by Fagerlund and Mitchell (1944)in their check list of plants in the HawaiiNational Park.

The map in Figure 1 shows ' the probablegeographic range of tomentosum as it existstoday. Sites collected during the present studyare indicated by solid circles. These do notdiffer materially from earlier collections recordedin the herbarium of the Bishop Museum. Sitesrecorded by earlier collectors, but not checkedduring the present study, are represented bysolid circles enclosed in rings. The open circleshows the locations of hybrid populations onOahu which will be considered later. Shadedportions of the map show the approximate areasin which the average annual rainfall is 20 inchesor less (Leopold, 1951:2).

In the case of the Oahu populations the ap­parent negative relation between rainfall andcollection sites is quite significant, since thetime available allowed for a careful search to bemade on an island-wide basis, and no popula­tions were found outside these dry areas. Else­where , owing to time limitations, only the drierareas were carefully studied. However, none ofthe collections in the Bishop Museum for whichlocations are recorded, appears to have beencollected outside the low rainfall areas, and itseems likely that in the neighbor islands, as inOahu, rainfall is a primary factor limiting therange of the species.

The negative relationship between rainfalland habitat is also indicated by the altitudinal

N ative Hawaiian Cotton-STEPHENS 387

MAUl

eNIIHAU

MOLOKAI

I'----+-------t----+--~~---t--ILANA~~

KAHOOLAWE

HAWAIIAN IS LANDS

HAWAII

F IG. 1. Geograph ic range of Gossypium tom entosum Nutt. in the H awaiian Islands (1963) . Solid circlesind icate collection sites; those enclosed in rings represent sites of form er collections unch ecked during thepresent study. Th e open circle indicates site of hybrid popul ations. Shaded areas correspond to regions with anaverage annual rainfall of 20 inches or less.

range of the species. On Oahu rainfall risesrapidly with elevation, and tom entosum wasnot found above an altitude of 100 ft. On Lanai,a low island in the rain-shadows of Molokai andMaui, scattered populations were found extend­ing from sea level to almost 1000 ft. The col­lections from Molokai and Maui were obtainedbetween 100 and 250 ft. These differences inaltitudinal ranges agree quite well with thevegetation maps published by Ripperton andHosaka (loc. cir. ).

ISLAND HABITATS1. Oahu

As shown in Figure 1, tomentosum is foundmost extensively on the western coastal plainin the rain-shadow of the W aianae Range. Hereit extends in scattered populations from thesouthern extremity of the range , north of Bar­ber's Point , to the outskirts of N anakuli. N orthof this village is another population aroundMaile Point and extending for about 2 miles

inland along the Hakimo Valley. Elsewherealong the coast only scatt ered plants were foundaround Kaena Point ( from north of Makuaextending around the point to the north coast).South of N anakuli , tomentosum is found almostexclusively as an unders tory, along with Sidaspp . and occasional Opuntia, in Prosopis (ke­awe ) "scrub. It appears to grow best under par­tial shade, i.e., wherev er the stands of Prosopisare relatively thin. A similar habitat occursaround Maile Point, but there a semiprocumbentform (ecotype or plastic variant ?) has ex­tended away from the scrub to the edge of theexposed beach. Inland it extends along the Ha­kimo Valley as a component of mixed Prosopisand Leucaena scrub. On the whole the popula­tions are found most commonly on the coastalflats, extending a little way up the slopes of theWaianae Range, but not ascending to a heightof more than 100 ft . On the ocean side theyrarely extend to the strand; the Maile Pointpopulation is exceptional in this respect.

388 PAOFIC SOENCE, Vol. XVIII, October 1964

Native Hawaiian Cotton-STEPHENS

A relic population occurs at the southernlimit of the Koolau Range, west of MakapuuPoint. Earlier records suggest that this popula­tion may once have extended farther west, atleast to Koko Head and possibly as far as Dia­mond Head. All the area west of Koko Head isbeing absorbed rapidly in housing develop­ments. The relic population is found along theroadside and extending inland to the west of theMauka Kai golf course. Here the former coverof Prosopis has been cleared in recent years andthe present habitat is obviously not a naturalone. A small population is also found as acomponent of Prosopis scrub inside DiamondHead Crater.

Two other interesting features of the habitatare worth noting at this time, since they applyto the other islands also. Without exception thewild cotton was not found growing in friablesoil, but always rooted deeply among outcropsof volcanic boulders, presumably the results ofancient lava flows. It was always found in as­sociation wiih.Sida, but was far more restrictedthan the latter in range and habitat. Threedifferent habitats on Oahu are illustrated inFigure 2. ,

2. Molok~i

According to Degener (1937: fam.22l), to­mentosum is commonly found in the dry south ­west end of the island, but is rare elsewhereexcept in the Kawela area, east of Kaunakakai.Unusually heavy rains prevented a visit to themain region, which is only accessible by tracescrossing the pineapple plantations west of Mau­naloa. The most recent collection from this areaappears to be Degener no. 9589 (Bishop Mu­seum) which was collected at Kamakaipo in1928.

Two populations, both of limited size, werefound along the coastal region between Kauna­kakai and Kawela . One of these occurred on amoderate slope about 50 fr above the highway, .2 miles east of Kaunakakai under a thin stand

389

of Prosopis. It was absent among the tallerstands bordering the highway and did not extendto an elevation of more than 100 fr inland. Theother population consisted of thinly scatteredplants rooted among large volcanic boulders lin­ing the sides of anini Gulch in the Kamiloloa­Alii Pond district. The population extendedfrom approximately 150-250 ft elevation. Atlower levels, plants were not found among thedense stands of Prosopis, nor at higher levelswhere Prose-pis was replaced by Leucaena. Noother populations were found in a search ex­tending as.far east as Kamalo.

3. Lanai

The range of tomentosum appea rs to begreater on Lanai than on any of the other islands.At sea level on the south coast around ManeleBay and near the east coast in the Keomukudistrict there are areas where it forms an almostsolid understory in tall Prosopis scrub. At higherelevations the populations thin out , and in theneighborhood of 1000 ft scattered plants occurin quite exposed positions, rooted on old lavaflows among low and sparse vegetation. In suchopen habitats tomentosum occurs as a sprawlingor semiprocumbent shrub and the characteristicromenrose surface of stems and leaves becomesintensified . Time did not permit collection onthe north coast of the island, which is not readilyaccessible. A collection from this area (Awalua)was made in 1961 by Kondo (nos. Ib and lcin the Bishop Museum) . It seems likely that i tis a common plant all around the periphery ofthe island in those areas which have not beenbrought in to pineapple cultivation.

4. Maui

No collections have been recorded from theeastern, and geologically much younger, regionof this saddle-shaped island. The herbarium inthe Bishop Museum has two collections, bothmade by Degener (nos. 3650, 17624), in ornear Pohakea Gulch, which is situated above

FIG. 2. Typical habitats of G. tomentosum on Oahu . Photographs by C. M. Rick.(a) Under Prosopis cover, near Barber's Point(b) Volcanic boulders in dry gulch, near Kahe Point(c) Exposed beach, near Maile Point

390

the eastern coastal plain on West Maui. In 1962another population, 10 miles west of this area,near Ukumhame Shaft, was collected by Mr.Craig Whitesell. According to his notes, thepopulation was scattered over 2- 3 acres atabout 250 fr elevation. This population was notlocated during the present study, but plantswere found in the Pohakea Gulch region at anelevation of about 100 ft. These occurred undera thin cover of Prosopis immediately above acane field and extending up into the gulch .

Most of the dry area in the "saddle" of theisland which is shown in Figure 1 is in canecultivation. Judging by the habitat of tomen­tosum on the other islands, the only likely areafor its occurrence on East Maui would be thedry southernmost region lying between Makenaand Kamanamana Point. Its vegetation is com­posed principally of tall Prosopis scrub withfrequent Opuntia, which is traversed in placesby bare, or almost bare, lava flows. This areawas visited but no tomentosum was found.

5. K ahoolawe

This island is uninhabited and has been usedfor some years by the U.S. Navy as a target forbombing practice. Its low-altitude location inthe rain -shadow of Maui and a past history ofheavy overgrazing combine to make it the mostbarren of all the major islands in the group.From the air it appears as a low plateau, prac­tically devoid of vegetation, with dry scrub lin­ing the steep gullies which surround its coast.Fifty years ago Forbes (l91 3a: 7), on the lastrecorded botanical exploration of the island,found a population of tom entosum near thesouthwest end.

6. Hawaii

Three areas which would seem to offer appro­priate habitats for the establishment of thespecies were searched without success:

( a) The dry coastal flats north of Kona Air­porr , Kailua

(b) The area bordering the coastal road be­tween Kealakekua Bay and the City ofRefuge in the South Kona District

( c) A small area between Honuap o and Pu­naluu Beach in the southern Kau District

PACIFIC SCIENCE, Vol. XVIII, October 1964

Time did not permit a visit to the Kau Desertand Hilina Pali areas which, as noted earlier, mayhave provided the necessary combination of alti ­tud inal range and vegetational type for Mac­Caughey's observations.

CLI MATE AND "SOI L"

The climatic conditions to which tomentosumis adapted would app ear to differ rather sharplyfrom those under which the wild forms ofhirsutum flourish in the Caribbean. Honoluluweather records from 1948-1960 indicate thatthe average temperature on coastal Oahu varies(in round figures) between 70 and 80 F, witha mean of about 75 F, and a diurnal range of9 F. The winter (short-day) months tend to becool and wet, though the monthly distributionof rainfall is very erratic. In contrast, the Carib­bean climate has a higher mean temperature,and shorr day length usually coincides with apronounced dry season and cooler night tempera­tures. The Caribbean cottons grow vegetativelyduring the long wet days, and flower and setseed during the dry season .i-Flower initiationseems to be determined in part by day lengthand in parr by. night temp erature (Mauney andPhillips, 1963 ) , so that there is a seasonalflowering cycle. This regular cycle is missing intomentosum. Mrs. Sinclair (1885:23) noted thatit flowered the year round; and the herbariumspecimens in the Bishop Museum were collectedin every month of the year except December.During the present study it was found that inany population-at least from Febru ary throughMay-most of the plants are vegetative and theremainder may have young flower buds, openflowers, or ripe bolls. Seeds can therefore becollected over a long period, but only fromrelatively few plants at any given time .

Although tomentosum can be considered adry-land plant, it appears to be less xerophyticthan Caribbean hirsutum. Wild forms of thelatter species will often thrive around salt ponds,and immedi ately exposed to strong winds andsalt spray. Forms which grow in dry scrublandaway from the coast tend to be components ofmore open vegetation, or else to grow tall.Typically they are not found as an unders toryamong taller plants. In contrast, the most vig-

Native Hawaiian COttOn-5TEPHENS

orous stands of tomentosum were found underlight shade.

The virtual restriction of tomentosum to oldvolcanic outcrops, as opposed to friable soil,suggests that it possibly may have rather special­ized physical and nutritional requirements. Mac­Caughey (loc. cit.) included it in a list ofspecies which he considered to be particularlyadapted to the colonization of lava flows andwhich were characterized by certain xerophyticfeatures . Some of these features are clearly ap­plicable to tomentosum (viz., woody perennialgrowth form, with slow growth and deep rootpenetration; foliage often pubescent ; and atendency to assume a decumbent habit on baresubstrates) . He also pointed out the extremelyxerophytic condi tions which are generated onrecent lava flows through a combination ofhigh evaporation, free drainage, and rapid heat ­ing of black or almost black surfaces. However,these conditions app ly particularly to recent lavaflows, and in the present study no tomentosumwas found in those areas ( Hawaii and EastMaui )to which recent flows are restricted.

It seems likely that some of the difficultiesof growing the species in culture may be as­sociated with (a) failure to provide sufficientlyrapid drainage, (b) too high a mean tempera­ture, and (c) too acid soil conditions. Withregard to the third factor, MacCaughey (1917 :408) noted that soils derived from Hawaiianlava flows have a far higher proportion of basicconstituents than comparable mainland soils(64 % as compared with 19%, according to hisfigures) . The following analysis of igneous rocksin Hawaii was obtained from "Handbook ofHawaiian Soils" (1935):

Average of 56 Analyses of Lavas fromIsland of Hawaii

Si02 50 N a20 3 3Ab03 14 K20 1Fe203 3 Ti 202 3FeO 9 PZ05 0.5MgO 8 MnO 0.1CaO 9

MORPHOLOGICAL VARIATION

Those morphological characteristics of to­mentosum which distinguish it taxonomically

391

from the other New World species of Gossyp­ium (long anther filaments , partly fused inpairs; absence of leaf nectary; inte nse yellowflower color; undifferentiated and strongly ad­herent seed fibers) were found to be quiteuniform. On the other hand, characters whichprevious experience had shown to be rathervariable ( leaf shape; bracteole form and dis­section; degree of pubescence ; plant habit)were found to be extremely variable . There waslittle if any tendency for these variations tofollow a geographical pattern; i.e., it was notpossible to distinguish morphologically betweendifferent island races. In this respect, G. tomen ­tosum contrasts strongly with the native speciesof the Galapagos Islands (G. darwinii) , in whicheach island has tended to develop its own well­marked morphological race. It is somewhatsurprising that two archipelagos, of comparablesize and origi n, and offering similar arid habitatsto related colonizing species, should have pro­duced such different evolutionary results.

The nature of variation in leaf shape andbracteole form is illustrated in Tab le 1 and Fig­ure 3, respectively . The data show the consider­able range of variation within anyone popu­lation, and the extensive overlap that existswhen different populaiionsare compared. Varia-

""II,a"'1,a*~_'a,a,'

FIG . 3. Outline drawings, approximate half naturalsize, of tomentosurn bracteoles. All bracteoles wereobtained from open flowers. Top row, Oahu ; 2nd row,Lanai ; 3rd row, Moloka i; 4th row, Maui.

392 PACIFIC SCIENCE, Vol. XVIII, October 1964

TABLE 1

VARIATION IN LEAF- SHAPE IN 11 POPULATIONS OF Gossypium tomentosumCOLLECTED FROM FOUR DIFF ERENT ISLANDS*

(Measurements based on ten mature leaves per population)

L-Length of leaf in mm from pulvinus to tip of median lobeS-Length of sinus in mm from pulvinus to base of median lobeIndex-S expressed as a percentage of L

L S IndexMean Range

OAHU 1. Barber's Point-Kahe Point _ 84.12. Kahe Point-Nanakuli.... ..... .................. ... ... ..... ....... 78.8 -3. Maile Point (procumbent form ) 80.04. Maile Point (shade form) - 100.05. Makapuu Point _... 79.6

MOLOKAI 6. Kaunakakai.. ..... .... ...... .... .... ...... ...... .. ....... ..... .... ... ..... 74.77. anini Gulch (100 ft elev.) c.. ".. .. .. .... . .. 64.48. anini Gulch (200 ft elev.) 81.0

LANAI 9. Keomuku... ...... ....... ........................ ...... ... .... .. ..... .. .... 71.110. Manele.... ...... .... ... .......... .......... ..... ...... .. ........ ..... ....... 71.7

MAUl 11. Pohakea Gulch...... .... ................ ............. .......... ...... ... 71.1

32.230.829.039.432.4

28.824.734.6

32.431.2

33.0

38.339.136.339.440.7

38.638.442.7

45.643.5

46.4

31-4928-4930-4531-4636-47

27-5035-4536-49

38-5336-55

42- 51

dons in both characters appear to be essentiallyrandom. On the other hand, variations in pubes­cence arid plant habit were markedly correlatedwith local environmental conditions to whichthe plants happened to be exposed. Plants grow­ing in exposed situations usually had a sprawlingor semiprocumbent Habit, and the leaves werecovered with a dense tomentum giving them abluish-grey appearance . Under Prosopis coverindividual plants were found which grew as highas 9 ft, and the leaves were finely tomenrosewith a dusty green color.

Experimental studies have shown that in NewWorld cottons, pubescence and plant habit canbe influenced strongly by environmental con­ditions, particularly light intensity; both charac­ters are also sensitive to changes in genotypicbackground. For instance, a single major genedetermines the finely tomentose surface of to­mento sum. When the gene is transferred bybackcrossing to a hirsutum background, the leafsurface becomes densely hairy and phenotypi­cally indistinguishable from the hirsutum mutantform "Pilose." The degree of hairiness can alsobe modified to a lesser extent by transferring theplants from a shaded greenhouse to full sunlight.Comparative studies under controlled environ­mental conditions would therefore be necessary

-to determine whether the variation observed in

natural stands of tomentosum is phenotypic onlyor the result of ecotypic differentiation.

POLLINATION AND INTROGRESSION

1. The Primary Breeding System

It has been pointed out by Baker (1955 :347­349) and Stebbins (1957 :343-344) that anautogamous breeding system would be initiallyadvantageous to a colonizing plant species, sinceit would render the latter independent of pollenvectors. On the contrary, it would be most un­likely for appropriate pollen vectors to be in­troduced into a new habitat along with thecross-pollinated species dependent upon them.This argument is particularly pertinent if ap­plied to the colonization of isolated volcanicislands like the Hawaiian group.

All species of Gossypium are self-compatiblewith radially symmetrical flowers, large numbersof anthers, and a true floral nectary located in adeep circular groove lined with glandular hairsat the inner base of the calyx. The nectary canbe seen only under low-power magnification ofa vertical section of the receptacle. It is accessibleboth to long-tongued insects and to insects smallenough to crawl between the bases of the petals.Usually there are also extrafloral nectaries lo­cated (1) at the bases of the bracteoles and (2)

Native Hawaiian Cotton-STEPHENS

on the outer surface of the calyx alternating withthe bracteoles, and there is a leaf nectary on themidrib of the under surface of each leaf. It isthus possible for insects to obtain nectar withoutentering the flowers at all. These characteristicsdo not suggest floral adaptation to any specificinsect vector (Grant, 1950: 392 ).

In tomentosum extrafloral nectaries and leafnectaries are lacking entirely, .bur a true floralnectary can be seen in vertical section . Thereis reason to suppose that the latter is nonfunc­tional or only weakly functional. When thecorolla is removed from a fresh flower of bar­badense or hirsutum, a pool of nectar can beseen within the calyx cup, but the secretion isweak or absent in tomentosum. This observation,based on the relatively few flowers available atthe time of study, .was confirmed later by Mr.Frank Johnson. He informs me that only afraction of the flowers he examined appeared tocontain nectar . It seems likely, therefore, thatinsects would visit tomentosum flowers primarilyto feed on pollen or to gather pollen. Further,because a limited number of plants are in flowerat anyone time in tomentosum populations, theywould not be likely to furnish a main source ofsupply to pollen-gathering insects. Under thesecircumstances a mainly autogamous breedingsystem is to be expected, with visits by pollen­gathering insects restricted to temporary periodsof over-all pollen shortage.

In Central America and the Caribbean, therelatively small and scattered populations of wildand dooryard forms of G. hirsutum do not im­press the observer as being heavily stocked withpollinating insects. Those commonly found inthe flowers are small ants and beetles whichprobably function more effectively as agents ofself- rather than cross-pollination. The situationin tomentosum populations appears to be similar,though the number of observations which couldbe made was too small to be very reliable .Unusually heavy and persistent rains occurredthroughout March and well into April in thisnormally dry habitat; thereafter there was atemporary cessation of flowering until towardthe end of May. In the latter part of Aprilthe combined results of three separate searchesthrough the Oahu populations yielded less than50 flowers. It was noted that although honeybeesand small moths (occasionally) and carpenter

393

bees and scavenger flies (rarely) were vrsmngSida flowers in the immediate neighborhood,none of these potential pollinating agents visitedtornentosum flowers. Most of the latter wereentirely devoid of insects, though occasionalflowers containing a few small ants or fruit-budbeetles (C onotelus mexicanus) were seen.

These observations, though limited, do notsuggest that insects play an important role inthe breeding system of tomentosum. On theother hand , a strictly autogamous system is dif­ficult to reconcile with the fact that tomento sumflowers, like those of other wild forms of theNew World species, have long styles with thereceptive stigmatic surfaces borne high abovethe staminal column (cultivated forms usuallyhave short styles with the stigmatic surfaces incontact with, or immediately above, the starninalcolumn ) . An interesting feature of the tomen­tosum style is the fact that it is often recurved,assuming a crozier-like structure with the stig­matic surface nearly approximated to the srarni­nal column.

2. Th e Effects of Insect Introduction

In oceanic islands like the Hawaiian groupwith a numerically poor indigenous insect fauna(Zimmerman, 1948: 94-95 ), the introductionof beekeeping as a local industry could havepotentially disturbing effects on the taxonomy ofthe local flora. A likely example is provided bythe dooryard cottons (G. barbadense) , whichstill may be found in gardens and along road­sides on the islands. As early as 1812, cottonwas introduced into Oahu (Jones, 1937 :17)and, later , in the early 20th century, seriousattempts were made to establish it as a crop(Krauss, 1909:1-16). Commercial varieties ofSea Island (barbadense) and Upland (hirsutum)were both introduced without lasting success.Around 1857 the first shipment of honeybeesarrived from California (Eckert, 1951 :1). Ac­cording to Van Dine and Thompson (1908:8) ,Prosopis soon became the primary source ofnectar, and on the western side of the islandapiaries were moved to the coastal areas underthe shelter of the Prosopis forests, where manyof them are found today. During the past 10years this source of nectar has been seriouslydiminished by the activities of an immigrantmoth, Ithome concolorella, which destroys the

394

florets of Prosopis and certain other leguminous.shrubs (Namba, 1956: 100) . As a consequencethe relativel y flower-constant honeybee has beenforced to forage among a variety of nectar (andpollen) sources.

The village of Nanakuli is located on a \crescent-shaped coastal plain of western Oahu,bounded by the Waianae Range which juts intothe sea to the north at Maile Point and to the.south at Kahe Point. The lower slopes of therange are dominated by a zone of Prosopisscrub, and where this zone approaches the coast,Fopulations of tomentosum are very commonin the understory. Occasional barbadense plantsoccur along the coastal highway which runsthrough Nanakuli, and also in gardens in thevillage itself . In two small areas, (a) south ofPiliokahe Beach and (b) in a waste lot adjoiningthe Texaco Service Station in the village, Out­

lying plants of tomentosum and barbadense are. growing within 50 yards of each othe r. Less

than a quarter mile inland, two colonies ofhoneybees are established in hives under theProsopis trees. And In the areas where tomen­tosum and barbadense are in close proximity,two obviously hybrid populations are foundwhose taxonomic properties are illustrated bythe data presented in Table 2 and Figure 4.

Table 2 gives the results of scoring the popu-

PACIFIC SCIENCE, Vol. XVIII, October 1964

lations for four qualitative or serniqualitativecharacters which distinguish the two species.The scoring was necessarily limited to thoseplants which were flowering at the time thestudy was made. The 11 plants scored include 9different combinations of charact ers, none ofwhich was identical with either parental com­bination. The populations were therefore segre­gating for characters which distinguish the twospecies.

The plants were also scored for certain metri­cal characters which previous experience hasshown to be useful in discriminating betweenspecies of New World cottons. These are pre­sented as a scatter diagram in Figure 4, accordingto the methods developed by Anderson (1949:81-10 1) . The characters measured are listedbelow; methods of measurement will be foundin the Appendix to this paper:

Br. T.-Number of bract teethBr. D.-Bract dissection indexBr. S.-Bract size1. I.-Leaf indexP. 1.-PetallengthS. I.-Staminal index

In Figure 4 staminal index is plotted on thehorizontal axis, petal length on the vertical axis.The other characters are symboliz ed according

TABLE 2

HYBRID Co'rrox POPULATIONS AT NANAKULI , OAHU; SEGREGATION IN Q UALI TATIVE CHARACTERS

Symbols used : H ( toment um ); N e (l eaf nectary ); Y ( bright yellow peral ) ; R (petal spot ) . Presence of eachcharacter is indicated by ( +) , absence by ( 0 ) and intermediate condition by ( - ) .

H

tomento sum ... c... ....... ..... ...... .. ... ... ...... ....... ........... .. ..... ++

Hybrid N o.1 ..2................. ............ ..... ..... .................. .... +3..... ............................. ....... .................... 0

4 ..... .. .. . . ... . . . . ... .. .. . . . . ........ . ... . . .. . . .. . . .. . . . . . . .. 0

5 ..6 ..7 .8 .. . .. . . .. . . .. . . .. . ... .... . . .. . .... . .. . . .. . . .. . . .. . . . . . . . . . . .. 0

9 .10....... .... ........ ....... ..... ...... .... .. ....... .... .... ... +11 ..

.barbadense.... .. ... .. ....... .... ..... ....... ....... ...... .......... .... .. ... 0

o

Neoo

+

o

o

o++

y

+++o+++

+

+++

R

0 Parent rype; in Prosopis0 scrub south of Nanakuli

0 }Waste grou nd near servicestation, N anakuli

+

+ 1Roadside beh ind Piliokahe

JBeach, Nanakuli

+++ Parent type ; Dooryards,0 Nanakuli

N ative Hawaiian Cotton-STEPHENS

rothe key accompanying the figure. Solid circlesrefer to the parental species ( barbadense to theleft, and tomentosum to the right of the chart ) .Open circles represent the plants under study,the "Texaco" plants being distinguished fromthe "Piliokahe" plants by dots placed within thecircles.

It is evident that although most of the plantsresemble barbadense with respect to the charac­ters measured, they all deviate in one or morecharacters in the direction of tomentosum. Thiswould be expected if they were hybrids segre­gating from backcrosses of tomentosum to bar­badense. A few of the plants had open bolls,and the seeds they contained bore fibers of twodistinct kinds-medium to long lint fibers, moreor less adherent to the seed-coat ; and coarse,strongly adherent fuzz fibers. Both lint and fuzzfibers were light brown in color. These fibercharacteri stics are typical of barbadense X to­mentosum hybrids studi ed previously in culture.

Several visits were made to the hybrid popu­lations from the beginn ing of March th roughMay, but at no time was insect activity among ­them very great. The pollen-feeding beetle(Con otelus) was quite common inside the openflowers, but it is not likely that it would beeffective as a cross-pollinating', agent. A fewsmall ants were also found in the flowers fromtime to time , but the only "prospects" likely tobe concerned in natural crossing were the rarevisits by honeybees, and one solitary visit by asyrphid fly, which were observed. Similarly, itwas noted that Conotelus was common insidethe flowers of dooryard barbadense in the samearea, and rather infrequently honeybees wereseen to enter the flowers also. A ,few carpenterbees and hornets were observed around theplants , but their attention app eared to be con­fined to the exrrafloral necraries, and they werenot seen to enter the flowers. During the sameperiod honeybees in particular, syrphids, andoccasionally carpenter bees and small mothswere seen to be actively visiting the flowers ofSida and a variety of garden ornamentals in theneighb orhood.

Thus it appears that rather infrequent visitsby honeybees were most likely responsible forthe origin of the hybrid populations , and forthe subsequent backcrossing and intercrossingwhich have probably taken place. However, the

395

drfi-

e-0 • 6- ii-'" 0:-

~ iid ~0 df iiv

~~

0

'" 60 BO 100 120 140

KIT

Jr., . 6 6 0b.low 9 9_15 obo ... 15

"' ,0. 6 0 0ab ove 75 65 . 75 below es

Br. S. if a 0be low 40 40 .6 0 ab o.... 60

r.r. 0- 0 0above 45 3.... below 35

FIG. 4. Scatter diagram showing variation patternin hybrid populations at Nanakuli , Oahu. StaminaIindex plotted on horizont al scale, petal length on vet­tical scale. Other characters indica ted according to key.Further explanatio n in text.

relati vely few observations which could be madeon tom entosum provided no direct evidence thathoneybees, or any other pollen-gathering insects"visit flowers of this species.

LOCAL NAMES AND USEThe re are rwo Hawaiian names for Gossypium

tomentosum: maro (" yellow-green") and bul«hulu (" hairy hairy" ). Two independent sourcessuggest that the plant was used by the ancientHawaiians as a source of green dye for theirkapa cloth. Malo (1 903 :43 , 74), writing about1836, stated definitely that ma'o was Gossypiumtomentosum, and that its flower was used as adye to color "tapa and the loin cloths of thewomen etc." Bennett ( 1840 :217 ) , who was asurgeon on a whaling ship, stated that "a delicategreen-yellow dye" obta ined "from an infusion ofthe flowers of the cotton plant" was used fordyeing kapa in Oahu . Later in the same narrative(1 840 :255) he said: "Several exotic kinds ofthe cotton-shrub (pulu or soft of the natives)grow wild in the plains, and includ e that rarespecies, the yellow or nankeen cotton (Gossyp­ium religiosum) called by the natives maroa,"

Brigham (1911 :50,144) referred to Bennett'sstatement, and assumed that the latter had con-

396

fused cotton with Abutilon incanum, which alsohad the Hawaiian name malo and which also wasused as a dye. That Brigham was in error IS

suggested from the following considerations:

(l ) Bennett's use of the ( then ) acceptedLatin nomenclature in ident ifying thenumerous plants he described in hisnarrative, indicates that he was a com­petent botanist.

(2) Bennett stated explici tly that the flowerswere used as a source of the dye: accord­ing to Brigham it was the leaves ofAbutilon which were used.

(3) Th e name malo is applied both to G.tomentosum and to A. incanum. Thename is incomprehensible as a descrip­tion of either plant, but qui te under­standable if it refers to a common dyeingproperty.

(4) The word "nankeen" was used non­specifically in the 18th and 19th centuriesto describe a brown-fibered cotton. Itwas applied both to Asiatic and to N ewWorld cottons and could reasonably havebeen applied by Bennett to the brown­fibered tomentosum. Bennett 's identifica­tion of this species as "G. religiosum" isconsistent with other nomenclatur e ofthe same period. (A n obvious specimenof G. tomentosum, no. 12935 in the Na­tional H erbarium, W ashington, D.C.,which was collected in 1845 by the U.S.Exploring Expedition under the com­mand of Charles W ilkes, is labelled"Gossypium religiosum.")

(5) It has been known for some time thatthe flowers of the cotton plant cont ainpigments, once thought to be of potentialimportance to the dyeing industry (Per­kin, 1899:825) . Dr. C. R. Parks (1963)has recently made a chromatographi csurvey of these pigments and has shownthat the depth of the yellow color in thepetal is pr imarily determined by therelative amount of the flavonol pigment,gossypetin, which it contains in variousglycosidal forms. Further he has shownthat the petals of tomentosum have largeramounts of this pigment than those ofother species. (This explains the bright

PACIFIC SCIENCE, Vol. XVIII, October 1964

sulphur-yellow sh ade of tom entosumflowers, as compared with the lemon­yellow of barbadense and the creamshades of many hirsutum forms). Solu­tions of gossypetin glycosides are brightyellow in color, but separate out in green­ish crystals when concentr ated. Slightlyalkaline solutions produce a green dye.According to Bennett (loc. cir.), the"astringent water of the taro patch" wasused to morda nt the dye-possibly amat ter of pH adjustment.

The other Hawaiian name, hulu hulu ( "hairyhairy" ), does not seem to be a particularly aptdescription of the finely tomentose surface ofthe plant . One wonders whether the name maynor, in fact, be a corrupted version of hooluu,which, according to Brigham (1911: 171) is"the pr incipal Hawaiian word meaning to color. . . to dive into the water, to plunge into aliquid , hence to dye. . . ."

SUMMARY

1. The wild cotton of the Hawaiian Islands,G. tomentosum Nutt., has never been foundbeyond the limits of the eight major islands ofthe group. Today it is only known on six of theislands : N iihau; Oahu, Molokai, Maui, Lanai,and Kahoolawe. There is apparently no definiterecord of its occurrence, or former occurrence,on Hawaii, despite general statements to thateffect in the literature.

2. Within its current geographical range, thespecies is found only in dry areas wit h an averageannua l rainfall of 20 inches or less. Its altitudi­nal range on any particular island therefore de­pends on local topography and position relativ eto rain -shadows.

3. The most common habitat is as an under­story in thin Prosopis scrub, growing amongpartially weathe red volcanic boulders. Less fre­quently it is found in more exposed positions,i.e., near beaches or (at relatively high altitudes)among thin low scrub.

4. The species has not evolved morphologi­cally disti nct island races. Those morphologicalcharacters which differentiate it taxonomicallyfrom other species of Gossypium are remarkablyuniform. Oth er characters may vary apparently

N ative Hawaiian Cotton-STEPHENS

at random (leaf shape and bract form ) , or maybe associated with the particular environm ent inwhich the plant is growing (pubescence andplant habit ) .

5. In one area in Oahu two populations werefound of undoubtedly hybrid origin ( G. bar­badense X G. tomentosum') , The underlyingreasons for this situation are discussed.

6. Evidence is presented for the belief rh- tthe flowers of G. tomentosum were used by theancient Hawaiian people as a source of greendye.

ACKNOWLEDGMENTS

In the course of this study I have drawn freelyon the time, combined experience, and specialknowledge of the following people: Dr. O.Degener, W aialua, Oahu ; Miss Marie C. N ealand Mr. Alvin K. Chock, Bernice P. BishopMuseum; Dr. C. Lamoureux, Botany Depart­ment, University of Hawaii; Dr. Dale Habeck,Entomology Department, University of Hawaii ;Mr. Steph en Au and Mr.-A. W. Duvel, Depart­ment of Agriculture, Kauai; Mr. Henry Wiebke,Hoolehua, Molokai; Mrs. Juliette W entworth,Hawaii N ational Park, Hawaii; Mr. 1. W . Bryan,Kailua , Hawaii; Mr . Craig Whitesell, U.S. ForestService, Hilo, Hawaii.

I am grea tly indebted also to Mr. G. Yamaneand Mr. W . Bonsey for transport and help withthe location of collecting sites on Lanai andMaui, respectively, and to Dr. C. M. Rick forthe photographs reproduced in Figure 2. FinallyI wish to thank my host, Dr. J . B. Smith, forthe excellent facilities provided in the GeneticsDepartm ent, University of Hawaii , for his con­tinued interest in the study, and for "stage man­aging" my travel in the neighbor islands.

REFERENCES

ANDERSON, E. 1949. Introgressive Hybridiza­tion. W iley, N ew York. ix + 109 pp.

BAKER, H. G. 1955. Self-compatibility and es­tablishm ent after "long-distance" dispersal.Evolution 9 (3) :347-349.

BENNETT, F. D. 1840. N arrative of a whalingvoyage round the globe from the year 1833­1836. Vol. 1. Bentley, London. viii + 402 pp.

397

BRIGHAM, W . T. 1911. Ka kana kapa. The mak­ing of bark cloth. B. P. Bishop Mus. Mem. 3.iv + 276 pp ., 48 pI. + 29, 131 figs.

CHRISTOPHERSON, E., and E. 1. CAUM. 1931.Vascular plants of the Leeward Islands, Ha­waii. B. P. Bishop Mus. Bul. 81. 41 pp . +16 pI.

DEGENER, O. 1937. Flora Hawaiiensis. Fam.221: 7/3/37, with fig. (pr ivately published ) .

ECKERT, J. E. 1951. Rehabilitation of the bee­keeping industry in Hawaii. Final Rep. IRACProject N o. 19. 29 pp.

FAGERLUND, G. 0 ., and A. 1. MITCHELL. 1944.A check-list of the plants in Hawaii N ationalPark. Nat. Hist. Bul. N o. 9. Hawaii N ationalPark. 76 pp.

FORBES, C. N . 1913a. N otes on the flora ofKahoolawe and Molokini. B. P. Bishop Mus.Oce. Papers 5 (3-1) :1-10.

--- 1913b. An e n u mera t io n of N iihauplants. B. P. Bishop Mus. Occ. Papers 5(3-2) :17-26.

GRANT, V. 1950. The flower constancy of bees.Bot. Rev. 16 (7 ) :379-398.

HILLEBRAND, W . 1888. Flora of the HawaiianIslands. Williams & N orgate, London. xcvi +.673 pp. , 1 pI. 4 maps.

JON ES, M. 1937. The Marin Journ al. Paradise ofthe Pacific 49 (8) :17.

KRAUSS, F. G. 1909. A preliminary report oncotton experiments. Hawaii A grie. Expt. Sta.Press Bul. 24. 16 pp.

LEOPOLD, 1. B. 1951. Hawaiian climate: itsrelation to human and plant geography. Me­teorological Monographs 1 (3 ) :1-6.

MACCAUGHEY, V. 1917. Vegetation of Hawaiianlava flows. Bot. Gaz. 64 (5) :386-420.

MALO, D. 1903. Hawaiian Antiquities. (Trans­lated by N . B. Emerson) . Hawaiian Gazett eCo., Honolulu. 366 pp.

MAUNEY, J. R., and 1. 1. PHILLIPS. 1963. In­fluence of daylength and night temperatureon flowering of Gossypium. Bot. Gaz. 724(4) :278-283.

NAMBA, R. 1956. Descriptions of the immaturestages and notes on the biology of Ithom econcolorella ( Chambers) (Lepidoptera: Cos­mopterygida ), a pest of kiawe in the Ha­waiian Islands. Proc. Hawaii Ent. Soe. 16 ( 1) :95- 100.

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PARKS, C. R. 1963. Comparative studies offlower pigments in the genus Gossypium.( Ph.D. thesis , North Carolina State College,Raleigh, N . C. )

PERKIN, A. G. 1899. The coloring matt er ofcotton flowers. Jour. Chern. Soc. 75:825-829.

RIPPERTON, J. c., and E. Y. HOSAKA. 1942.Vegetation zones of Hawaii . Hawaii Agric.Expt. Sta, Bul. No. 89 :1-60, 3 maps .

ST. JOHN, H . 1954. Review of Mrs. Sinclair's"Indigenous flowers of the Hawaiian Islands ."Hawaiian Plant Studies 23. Pacif. Sci. 8 (2) :140- 146.

SINCLAIR, ( MRS.) F. 1885. Indigenous Flowersof the Hawaiian Islands. Sampson Low, Lon­don. 44 pp . (with facing plates).

STEBBINS, G. L. 1957. Self-fertilization andpopulation variability in the higher plants.Amer. N at. 91( 861):337- 354.

STEPHENS, S. G:1963. Polynesian cottons. Ann .Mo. Bot . Gdn. 50(l ) : 1-22.

VAN DINE, D . L., and A. R. THOMPSON. 1908.. Hawaiian honeys. Hawaii Agric. Expt. Sta.Bul. No. 17.21 pp . +1 pI.

WATT, G. 1907. Th e Wild and Culti vated Cot­ton Plants of the W orId. Longmans, London.x + 406 pp. , 53 pI.

WAWRA, H. 1872. Beirrage zur Flora der Ha­wai'schen Inseln. 158 pp.

ZIMMERMAN, E. C. 1948. Insects of Hawaii .Vol. 1. Introduction. Univ. Hawaii PressHonolulu. xx + 206 pp., 52 figs. '

PACIFIC SCIENCE, Vol. XVIII, October 1964

APPENDIX ·

Methods of measuring characters shown inFigure 4 :

Br. T .-The average number of teeth perbracteole, based on counts of 10 bracteoles.

Br. D.-Bract dissection index: S expressedas a percentage of L, where S is the distancefrom bracteole base to base of the sinuseson eith er side of the median tooth, and Lis the distance from bracteole base to apexof median tooth. Measurements averagedfrom three bracteoles each removed from aflower in bloom .

Br.S.-Bract size: The geometric mean ofbracteol e length and bracteole breadth. Av­eraged from three bracteoles , each removedfrom a flower in bloom.

I. I.-Leaf index: S expressed as a percentageof L, where S is the distance from leafpulvinus to base of medi an lobe, and L isthe distance from ·leaf pulvinus to apex ofmedian lobe .:Measurements averaged fromthree climax leaves.

P. I.-Petal length, measured from claw ofpetal to maximum distance on ourer edge.Averaged from three fresh petals fromdifferent flowers. .

S. I.-Staminal index : Maximum diam eter ofstaminal column expressed as a percentageof the length of the column. Measurementsaveraged from three flowers.