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I felt very privileged to visit Phu Luang Wildlife Sanctuary, and I can only hope that the conservation measures being taken there will allow others the opportunity to visit this unique and beautiful plateau.
ACKNOWLEGEMENTS. I would like to thank most sincerely the following people and organisations whose help with funding made this expedition possible. The Bentham-Moxon Trust; Studley College Trust; Mr. D. Clulow; Mr R. Bilton (McBeans Orchids Ltd); Mr. B. Rittershausen (Burnham Nurseries); Miss W. Rittershausen (The Orchid Review). My grateful thanks also to Dr P. Cribb, Dr G. Seidenfaden, Dr T . Smitinand, The Royal Forest Dept. in Bangkok, Mr N. Sornnakorn and my com- panions Dr F. Rasmussen, G. Kjellsson and Dr Chawalit Niyomdham.
THE UNDERGROUND ORCHIDS OF AUSTRALIA
Mark Clements & Phillip Cribb
The intimate role of fungi in the life cycle of orchids was discovered by the French scientist Noel Bernard at the turn of the century (Bernard, 1903). All orchids are now known to require a fungus, termed a mycorrhiza, to germinate successfully. The fungal partner supplies the orchid with essential nutrients, particularly simple sugars for growth. Whereas most orchids eventually produce green leaves and become less dependent upon, or even independent of, their fungal partner, a few are totally dependent upon this rela- tionship. These are popularly called the saprophytic orchids.
The most extraordinary of these ‘saprophytes’ are two species whose life style has become so modified that the plants germinate, grow and flower without ever coming above the surface of the ground. These are the famous Australian underground orchids Rhizanthella gardneri R. Rogers and Cryptanthemis slateri Rupp.
Both species consist of branching fleshy rhizomes that grow laterally in sand or soil about 8-20 cm (3-8 in) below the surface. The inflorescences arising from the apex of one or more of these rhizomes are covered in white or pink scales, the flowers being flesh coloured to maroon.
HISTORY. Rhitanthella gardneri was first seen in 1928 by a farmer, John Trott, while ploughing an area of rolled mallee near Corrigin
84
about 200 km (186 ml) to the east of Perth in Western Australia. In all he uncovered 36 plants in the area. During the next 40 years it was seen again only twice: once in 1940 when Trott again found a plant at Corrigin and in 1962 at Babakin when C. W. Bee also found a single specimen. By the early 1970s it was generally con- sidered to be extinct. However, through the perseverance of Alex George of the Western Australian Herbarium it was rediscovered in 1979 near Munglinup, some 500 km (3 10 ml) SE of the original site by John McGuiness (for an account of this see George, 1980). I t was found growing, as in its other sites, at the base of Melaleuca uncinata R.Br. in mallee scrub. Subsequent searches in the few remaining areas of M . uncinata similar to that at Munglinup, have revealed about 100 plants in a further 10 or so sites.
The second species, Cvptanthemis slateri Rupp, was discovered by E. Slater in November 1931 on the opposite side of the continent in New South Wales. He found it at Bulladelah, Alum Mt., amongst the roots of a plant of Dipodium punctatum ('J. E. Smith) R. Br. which he was lifting to transfer to his garden. I t has subse- quently been seen three times. Kesteven and Rupp relocated it two years later (1933), in the type locality, bringing to 12 the number of plants found a t that site. Subsequently, it was found in Lamington National Park, on the Queensland - New South Wales border, in a road cutting and also at Springwood in the Blue Mountains west of Sydney, where it was found in ground being prepared for the foundations of a garage. I t has not been seen now for nearly 20 years despite frequent searching. Unlike R. gardneri, it does not appear to be associated with a particular Melaleuca species, but it is found in Eucalyptus forest.
BIOLOGY OF THE SPECIES. The significance of the relationship between Melaleuca uncinata (Myrtaceae) and R. gardneri is still not fully understood. Recent research has shown that the mycorrhizal fungus found within the rhizome of R. gardneri also occurs on the papery surface of the roots of the Melaleuca (Dixon, 1982). However, this may be coincidental rather than of significance for there appears to be no evidence of this fungus being a parasite on the Melaleuca. Rather it seems likely the fungus feeds on the dead leaves of the Melaleuca which are abundant under every bush.
Both species have long, been thought to be self-pollinating (e.g. Dres- sler, 1981). However, a tiny fly (Megaselia sp.) has recently been caught emerging from the orifice of a flower of R. gardneri with pollen massulae adhering to its thorax (George, 1981). These have been confirmed as belonging to the orchid. Apparently, the fly is attracted to the flowering
85
head of R. gardneri by its faint scent. I t then, enters through the orifice above the flower-head presumably for food, inadvertently pollinating some of them. If it again visits another flowering plant cross pollination would result. The pollinators of C. slateri are as yet unknown. The large hard seeds of R. gardneri are thought to be dispersed either by small native mammals eating the capsule and the seeds passing through in the faeces or by white ants which are known to eat the capsules of the plant.
MORPHOLOGICAL COMPARISON. Through the courtesy of the curators of the National Herbarium New South Wales, Royal Botanic Gardens, Sydney and of the Western Australian Herbarium, we have had the opportunity to examine and compare material of both species preserved in alcohol. Several authors (Nicholls, 1965; Clemesha, 1968; Balogh, 1982) have commented on the similarity of the two species and indeed it has been suggested they may belong in the sa’me genus.
In describing Cryptanthemis, Rupp (1932) gave four reasons for con- sidering it distinct from Rhizanthella. He suggested that the sepals and petals of Cryptanthemis were membranous and the flower continuous with the ovary with the point of union quite obvious. Its sepals and petals are in fact fleshy and the point of union of the flower and ovary no more nor Jess obvious than in Rhizanthella gardneri. Secondly, the figure shows quite clearly that the sepals of Rhizanthella are only united towards the base and do not form a ‘tube or bell’ as Rupp suggested. His third distinction concerns the lip which he stated to be rather small and attached to a long claw in Cryptanthemis. Again, the accompanying illustrations show clearly that in both species the lip and claw are essentially similar. Finally, he stated that the column of Cryptanthemis is quite free and bears two lateral appendages (staminodes), However, in both species the col- umn is fused at its base to the base of the petals. Whilst agreeing that the staminodes of Cryptanthemis are obvious it is also apparent that these, albeit reduced in size, are alSo present in Rhizanthella gardneri.
Cryptanthemis and Rhizanthella do differ in some features, however (see Table 1). For example, each flower in Rhizanthella is subtended by a one-veined bract, the outer bracts surrounding the capitulum being 3- veined and much larger. All the bracts in Cryptanthemis are one-veined. The flowers of Cryptanthemis are indeed slightly larger than those of Rhi- zanthella and differ in having sepals with acuminate tips. The lip of Cryptanthemis is more papillose than that of Rhizanthella but of an essen- tially similar shape. We are, therefore, convinced that we are considering two closely allied species in the same genus. Since Rhizanthella is the
Rhizanthella gardneri. A, habit, X 1%; B, bract, X 3; C, lateral petal, X 12; D, flower, lateral view, X 6; E, flower, front view, X 6; F, flower, half-section X 12; G, column, front view, X 12; H, lip, X 18. R. slateri. J, habit X 1%; K, bract, X 3; L, lateral petal, X 6; M , flower, lateral view, X 6; N, flower, front view, X 6; 0, flower, half-section, X 9; P. column, front view, X 12; lip, X 18.
87
TABLE 1 see page 87 Character Rhizanthella slateri Rhizanthella gardneri
Habit subterranean saprophyte subterranean saprophyte Rhizomes: roots elongated, branching, roots elongated, branching; roots
absent or much reduced absent or much reduced Inflorescence a very condensed, conical a concave capitulum
caaitulum ____
Flowers small, white and maroon small, white and maroon Sepals basally fused basally fused Petals one-veined, ovate, adnate to one-veined, ovate, adnate to
column towards base column towards base Lip fleshy, conduplicate, hinged to fleshy, conduplicate, hinged to
column-foot. entire column-foot. entire ~~ ~ ____ ~~
Spur absent absent Colurnn-foot short short Column Stigma
fused to petals in basal part a shallow cavity with a raised rim rim
fused to petals in basal part a shallow cavity with a raised
~~
Staminodes obvious, elongate present but very short Anther , erect, fixed with a prominent erect, fixed with a prominent
conical connective ’ conical connective
earlier generic name we hereby transfer Cryptanthemis to the genus as follows:-
Rhizanthella slateri (Rupp) M. Clements et Cribb comb. nov. Cryptanthemis slateri Rupp in Proc. Linn. SOC, N.S.W. 57: 58 (1932). Type:
N.S.W., Alum Mt., Bulladelah, Nov. 1931, Slater (NSW, holo.; K, part of holo.!)
THE GENERIC AFFINITIES OF RHIZANTHELLA. The generic affinities of Rhizanthella (including Cyptanthemis) have long been the cause of con- siderable speculation, possibly due to the lack of access to adequate preserved material. Rogers (1928) in describing the genus Rhizanthella placed it in its own subtribe Rhizanthellinae of the tribe Gastrodieae. Lavarack (1971 & 1976) and Dressler (1981) have maintained this attri- bution on the basis of the plants having mealy pollen, partially fused perianth segments and a saprophytic habit. More recently, the affinities of Rhizanthella have been questioned by Balogh (1982), who considered it most closely related to Cephalanthera, a north temperate genus in the subtribe Limodorinae of the tribe Neottieae. This conclusion was based on supposed similarities in column, anther and pollen morphology. We have compared the floral structure of Rhizanthella with representatives of the genera Gastrodia in the Gastrodieae, Cephalanthera, Limodorum and Aphyllorchis in the Limodorinae and the results can be seen in Table 2. The supposed resemblance of Rhizanthella to Gastrodia lies in the sapro- phytic habit and in the fused floral segments. However, in itsxolumn structure in particular, in its rigid erect anther, prominent connective and simple lip lacking calli and attached to the column-foot by a carti-
88
TA
BL
E 2
C
hara
cter
G
enop
lesi
um
Cep
hala
nthe
ra
Lim
odor
um
Aph
yllo
rchi
s G
astr
odia
H
abit
te
rres
tria
l sem
i-
terr
estr
ial a
utot
roph
ic
terr
estr
ial
sapr
ophy
te
terr
estr
ial s
apro
phyt
e te
rres
tria
l sa
prop
hyte
sa
prop
hyte
(c
hlor
ophy
llus)
R
hizo
mes
: roo
ts
abbr
evia
ted,
som
etim
es
shor
t; ro
ots
thin
, th
ick,
ver
tical
ly
shor
t, th
in s
light
ly
elon
gate
, thi
ck, f
lesh
y;
bran
chin
g; r
oots
abs
ent
spre
adin
g ra
dial
ly
elon
gate
; ro
ots
v. t
hick
fle
shy;
roo
ts s
hort
ro
ots
abse
nt o
r th
in
flesh
y, e
long
ate;
fle
shy,
spr
eady
rad
ially
el
onga
te a
risi
ng r
adia
lly
spre
adin
g ra
dial
ly
at b
ase
of in
flore
scen
ce
Infl
ores
cenc
e ra
cem
e ra
cem
e, w
ith l
eave
s ra
cem
e ra
cem
e ra
cem
e Fl
ower
s sm
all,
red,
pin
k &
la
rge,
whi
te, y
ello
w o
r la
rge,
cre
am, m
auve
or
smal
l to
larg
e, m
auve
la
rge,
bro
wn,
cre
am o
r
Sepa
ls
free
fr
ee
free
fr
ee
fuse
d Pe
tals
3-
vein
ed, l
ance
olat
e 3-
vein
ed l
ance
olat
e 3-
vein
ed, e
llipt
ic-
1 ve
ined
, la
nceo
late
- 3-
vein
ed, f
uscd
to
peta
ls
yello
w
pink
pu
rple
or
cre
am
mau
ve
lanc
eola
te
ellip
tic
Lip
fle
shy,
con
dupl
icat
e,
thin
-tex
ture
d, f
lat o
r th
in-t
extu
red,
fla
t, la
nceo
late
-elli
ptic
th
in, f
lat
with
2 s
ets
of
hint
ed t
o co
lum
n-fo
ot
with
inc
urve
d m
argi
ns,
incu
rved
, m
argi
ns
fles
hy, s
acca
te,
calli
, one
bas
al t
he
atta
ched
to b
ase
of
adna
te to
bas
e of
ob
scur
ely
3-lo
bed
othe
r ne
ar t
hr a
prx:
co
lum
n an
d sh
ortly
co
lum
n, 3
-lobe
d ob
scur
ely
3-lo
brd
adna
te a
t ba
se.
3-lo
bed
Spur
ab
sent
pr
esen
t in
a r
educ
ed
pres
ent
abse
nt
abse
nt
Col
umn-
foot
pr
esen
t ah
sent
ab
sent
ab
sent
C
olum
n fr
ee
fusc
d to
has
r of
lip
fuse
d to
bas
e of
lip
and
fr
ee
free
form
spur
sl
ight
ly r
aise
d a
shal
low
cav
ity
Stig
ma
shal
low
, hi-l
ohcd
ra
ised
, 3-p
arti
tr
rais
ed, 3
-par
tite
Stam
inod
es
obvi
ous,
elo
ngat
e ;th
sent
pr
esen
t m
uch
redu
ced
abse
nt
abse
nt
Ant
her
& e
rect
, fix
ed w
ith a
cr
crt,
atta
ched
to a
er
ect,
atta
ched
to a
er
ect,
atta
ched
to a
er
ect,
atta
ched
to
ii
prom
inen
t co
nica
l li1
;irnc
nt a
nd n
itrhi
lr,
fila
men
t an
d m
obilr
, fi
lam
ent a
nd m
obile
, sh
ort
fila
men
t and
co
nnec
tive
lyin
g in
it Ir
mii
nal
lyin
g in
a t
erm
inal
ly
ing
in a
ter
min
al
mob
ile.
Iyiu
g in
a
cmca
vr c
linitn
driu
ni
CO
IIC
~V
C cl
inan
driu
m
conc
ave
clin
andr
ium
te
rmin
al c
onca
ve
co
clin
iindr
iuni
0
lagenous hinge, Rhizanthella appears quite distinct from any member of the Gastrodieae. Furthermore, in Gastrodia the petals are fused to the sepals and the latter are fused almost to the apex forming a tube with a narrow mouth. In contrast the sepals are only shortly fused, a t the most, in Rhizanthella and the petals are shortly fused to the column rather than to the sepals.
Cephalanthera and related genera have an erect terminal anther, articu- lating on the slender filament, set in a deep clinandrium at the apex of the column. The lip at its base is fused to the basal margins of the column and is not hinged. In Limodorum, the lip i s also spurred. The flowers have thin-textured segments which are free from each other to the base. The sketches given by Balogh ( 1982) comparing Rhizanthella and Cephalunthera columns are oversimplified and consequently misleading. She also com- pares the pollinial structure and pollen surface morphology of these genera. They are indeed rather similar but no more so than other genera of the Keottieae.
Dressler & Dodson (1960) suggested that the affinities of Rhizanthella might lie with the Australian Diurideae, although the former later changed his mind (Dressler, 1981). \.Ye consider that the affinities of Rhizanthella, so far only recorded from Australia, deserve reconsideration especially as the Gastrodieae aye predominantly of Asiatic and the Lim- odorinae of Sorth Temperate/Asiatic distribution.
The column structure of Rhizanthella is reminiscent of that found in the saprophytic orchid Genoplesium baueri and in Prasophyllum sect. Micran- thum. These small flowers are also similar having a simple hinged lip attached to a short column-foot and are pollinated by similar insects, i.e. small Diptera spp. In both Genoplesium and Prasophyllum a short stipe attaches the viscidium to the pollinia but we have seen no similar struc- ture in Rhizanthella. We are also at a loss to explain the rhizomatous habit of Rhizanthella, but it must be said that whereas stem-root tubers are present in most Diurideae some lack them e.g. Rimacola. However, it has been shown that Rhizanthella uses a similar mycorrhizal fungus to the Diurideae. (Warcup pers. comm.). The likelihood of Rhizanthella being a member of the Diurideae Endlicher, which is the best represented tribe in the Australian orchid flora, seems to us a suggestion that warrants further investigation.
THE CONSERVATION OF RHIZANTHELLA. The two species of Rhizanthella are rare plants. I t could be argued that their rarity is an illusion because underground orchids are never easy to find. However, we know in the case of R . gardneri that it only grows in association with Melaleuca uncinata, a species formerly abundant and widespread throughout much of south-west Western Australia but now greatly reduced in its extent be- cause of agriculture, the mallee country in which M . uncinata grows being prime wheat growing country in that part of Australia. Consequently, less remains nowadays. Again, R. slateri is associated with a (potentially) endangered habitat, for the forests of eastern Australia continue to be
90
felled at an alarming rate. Because so little is known about the habitat requirements of R. slateri it is possible that sites in which this orchid occurs are being destroyed for agriculture, housing, or forestry.
It is therefore of considerable interest to note that attempts to grow R. gardneri from seed, both symbiotically and asymbiotically, are distinctly promising (Warcup. pers. comm.). Although news of the successful cul- ture of Rhizanthella is keenly anticipated the only real hope for these plants lies in the protection of their natural habitats. We are pleased to report that such is the case in Western Australia where several areas in which R. gardneri grows have been set aside as reserves specifically for the protection of the species. The search for R. slateri in the east of the continent continues and we eagerly await news of its rediscovery.
ACKNOWLEDGEMENTS. We wish to thank Don Blaxell, Royal Botanic Gardens, Sydney, New South Wales, Kevin Kenneally, Western Aus- tralian Herbarium and Alex George, Bureau of Flora & Fauna, A.C.T. Part of this research was funded by the Sainsbury Trust through the Bentham-Moxon Trust.
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Balogh, P. (1982). Rhizanthella R. S. Rogers, a misunderstood genus.
Bernard, IK. (1903). La germination des orchidtes. Comp. Rend. i\cad.
Clemesha, S. C. (1968). Saprophytic orchids of Australia and Sew Zea-
Dixon, K. W. (1982). Rhizanthella in 1981. The Orchadian 73: 99-100. Dressler, R. L. (1981). The Orchids: Natural History and Classification.
Harvard University Press, Cambridge, Massachusetts, USA. Dressler, R. L. and Dodson, C. H. (1960). Classification and phylogeny
in the Orchidaceae. Ann. Miss. Bot. Gard. 47: 25-68. George, A. S. (1980). Rhizanthella gardneri R. S. Rogers - the underground
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