lndia has a diversified cl imate comprising the Thar desert

with hardly any rainfall to Meghalaya having the highest rainfall in

the world. The existence of a tropical to temperate cl imate along

the lndo-gangetic plains to the highly elevated Himalayan ranges has

resulted in a diversified flora. By virtue of its location in the tropical

belt, with some patches of evergreen rain forests still existing in its

territory and inspite of being unscrupulously exploited, lndia is very

rich in i ts f l o ra . Having a history of thousands of years of cultural

tradit ions, the inhabitants of this land have developed a rich store

house of knowledge about the vital uses of the local plants. The

reckless course o f modernisat ion resulted not only i n the loss of

many o f these nat ive p lants, but a lso in the loss of indigenous

knowledge about the uses as wel l as tqe correct identity of many

local species.

In the present day, the knowledge of plant species is based

on morphological, biochemical, cytological and biotechnical analysis in

co-ordination with many other domains of science. Plant taxonomy is

one of the branches which comprehends all others and has a unique

posit ion in biology. I t will have a continued role to play and will

make significant contributions with regard to our understanding of the

different kinds of plant species. In ; the recent years, it has undergone

a paradigm shift f rom science based merely on observations to

science based mainly on theory and experiments.

The family Polygalaceae has the distinction of an extremely

natural taxon with its unique floral theme and micromorphological

features including those of seeds and pollen grains. It includes about

twelve genera and eight hundred species of herbs, shrubs and small

trees and is distributed along the tropical to arctic zones. The

distinguishing features of this family include the zygomorphic flowers

that adapt a Papilionaceous character, a many lobed subterminal crest

of the dorsal petal, the appendaged hairy seeds and the multicolpate

- stephanocolporate pollen grains.

The generic name Polygala, Linn. is derived from two Greek

words- Poly meaning 'much' and gala meaning 'milk', depending on

the property assigned to the plants in increasing the milk production

of animals (Barton and Castle, 1877). The family is therefore

commonly called "milk wort" family. The medicinal properties of certain

species of Polygala, Linn. are commendable. Most of the members t

are used as tonic and expectorant (Kirtikar and Basu, 1981; Agarwal

and Ghosh, 1985). The root extract of these plants possesses a

substance closely related to saponin. The family is also known as

"snake-wort" family since the root extract of P. arillata, Ham. and P.

elongata, Klein ex Willd. are used as an antidote to snake bites. The

roots of P. crotalarioides, Ham.; P. chinensis, Linn. and P. sibirica,

Linn. are used medicinally in catarrhal infections. The leaf infusion of

P. chinensis, Linn. is prescribed for asthma and chronic bronchitis.

The leaves of P. chinensis, Linn. and the leaves, shoots and roots of

P. japonica, Houtt. and P. tenuifolia, Willd. are eaten after boiling in

several changes of water. Thus most of the species belonging to this

family are economically important due to their medicinal value. The

relevance of these plants as valuable sourcebof medicine is well \

known from time immemorial, though not yet properly studied and

optimally utilized.

For the present study, plants were collected from different

regions of Kerala, Karnataka, Tamil Nadu and Maharashtra. Eighteen

species of Polygala, Linn., and one species each of Salomonia, DC.

and Xanthophyllum, Roxb. were collected. The regions from where

these plants were collected fall in the Peninsular Indian region and

lie between 8O5' and 1g051' N and 70°52' and 84O40' E, covering an

area of 6,43,426.130 sq.km. The altitude ranges from sea level to

2,695 meters. The climatic conditions also vary and the temperature

goes down even less than O°C in cold seasons in the hill stations

and rises up even more than 3g°C - 42OC in summer in dry areas of

the plains. Mukherjee (1958) has reported 4 genera and 31 species . ,

' lndi,a, of which 3 genera, 20 spec+es and 5 varieties were

collected from the places selected for the present study. The shape

and size of the leaves and gradation of the indumentum are usually

too variable to be trusted. The variability in these characters appears

to be far greater than that is accounted for in the literature. Earlier >

this resulted in the creation of a fairly large number of names. Most

of the intraspecific taxa described by the previous researchers which

were based on unstable characters have now been merged under

respective species.

The most comprehensive study dealing with the morphology

and taxomony of Polygalaceae is st i l l Chodat 's (1890-1893)

"Monographia Polygalacearum': Since then many valuable contributions

towards the f lor ist ic study of this family have been made by

Gagnepain (1 908). Rehder and Wilson (1 91 4), Craib (1 91 9). Mukherjee

(1955, 1958), Patel (1959). Phatak and Oza (1959), Larson and

Skarvla (1961). Shah (1961). Adema (1966), Chandrabose (1968),

Burtt (1973). Dar (1973). Dickson (1973), Das and Banerjee (1974).

Banerjee and Banerjee (1975). Paul and Kharbanda (1976), Smith and

Ward (1976), Sharma and Mehra (1978), Meijden (1982), Merlee

Teresa ( 1 988), Merlee Teresa and Liza (1999) and Merlee Teresa

and Rekha (2000). In the present investigation, an effort is made to

study foliar rnicromorphology, histochernistry, embryology, palynology

and seed morphology of se lected members of the family

Polygalaceae.

The purpose of studying comparat ive morphology i s to

discover the natural relationship of plant categories result ing in a

system, of classification. Morphological characters can easily be seen

and therefore we can appreciate their var iabi l i ty wi th much more

faci l i ty than other kinds of features. Although morphology of the

angiosperms is considered to be properly known. it is not true for all

the groups. Of late, in the taxonomic treatment of species, more

stress is la id on the vegetat ive characters, especial ly population

analysis based on stat ist ical data. Indeed, there i s evidence to

believe that plant morphology must have been one of the oldest of

man's academic persuits.

Carlquist (1961) states that the leaves of plants provide a

var iety of morphological and anatomical features which can be

employed as usefu l taxonomic characters. Leaves, probably

anatomically the most varied organ of angiosperms, have provided

very valuable help in taxonomic matters. According to Stace (1989),

leaf characters are extensively employed for the recognition of species

in many genera. Solereder (1908), was the f irst to point out the

signif icance of stomatal characters in the delimitation of taxa. The

number, position and structure of subsidiary cells bordering the stoma,

level o f stomata in the epidermal tissue, the number of stomata per

unit area, their arrangement, size and structure contribute very much

for taxonomic considerat ions. The stomatal index and stomatal .p -,

f requency of (the individual species within the genus are different

except in rare cases, which become useful diagnostic features.

The pharmacognost ic value of epidermal features and

palisade ratio has long been recognised (Datta and Mukerj i , 1952; \

Wallis and Forsdike, 1938) and is relevant even today (Metcalfe and

Chalk, 1979; Baranova, 1992).

Histochemistry is a science as o ld as history i tself as

quoted by L ison (1936), one of the forefathers of histochemical

techniques. Cytochemical localization technique , as histochemistry is

called nowadays, has emerged as a powerful tool in the hands of

plant scientists. Botanical histochemistry, although relatively new. is a

fast developing area of research, combining histology and analytical

biochemistry. Histochemical techniques help us to identify and localize

biochemical substances of the cell wall, cytoplasm and nucleus in the

cells and tissues (Johansen, 1940).

Histochemical procedures are based on biochemical methods

and the ultimate aim of histochemistry is to express the chemical

data in morphological terms. This can be done e i ther directly as

amount per cell or indirectly by co-relating chemical change with

morphological change (Jensen, 1962).

The purpose of microscopic histochemistry in the present

work is to localize and identify the nature of primary metabolites

present within the foliar epidermis, specifically the stornatal complex.

These biochemical compounds are present in every cell of the plant

body, but are more readily available and easily observed in the

epidermal tissue of the leaves.

Pollen giain constitutes another vital plant unit, invariably

present in all sexually reproducing angiospermic taxa, and it performs \

the physiological function of reproduction. From the work of

Wodehouse (1935). Erdtman (1952) and a host of others, i t is now

known that the exine is the projectile of the essential aspects of

pollen morphology. The structure and surface sculpturing of the exine

are very complex but specific for the various taxa of plants. The

exine of pollen is endowed with such stable morphological characters

which are genetically fixed and do not get inf luenced by the

environmental fluctuations (John and Skvarla, 2000). These characters

are specif ic for different genera and may vary from species to

species. Diversity of the aperture types and multiplicity of the exine

sculpturing make them highly useful characters of taxonomic value

(Nair, 1965, 1966).

Presently pollen morphological characters are invariably used

to substantiate taxonomic revisions and to draw systematic

conclusions. Despite the basic simplicity of the technique of pollen

analysis, they should be observed under higher magnifications for

their accurate identification. The scanning electron microscope has

proved to be the most useful tool for palynologists, as it enables one

to have a detailed look at the sculpturing of pollen exine. The study

of pollen morphology has assumed great significance in the realm of

morphological and comparative botany. For the past three centuries,

pollen and spores, representing an essential genetic bridge between

one generation and the next, have been the object of innumerable

microscopical investigations.

* The structural organisation with a homogeneous endoexine

and a heterogeneous ectoexine consisting of the radial columella, the

tecturn and the ornamentation patterns not only are of use in

providing rigidity and tenacity to the protective exine wall, but also

provide information of significance in taxonomy and phylogeny. From

the studies conducted over years, it is now real ised that the

morphology of pollen as contained in the exine wall may be resolved

into f i ve groups of characters, namely: germinal aperture, exine

ornamentat ion, exine strata, s ize and shape in the order of their

importance. A combinat ion of these features provides a particular

taxon an entity in itself. This is the priniciple on which the application

of pollen morphology in taxonomy and phylogeny is based. In studies

involving hybrids and their parents, the pollen grains have provided

interest ing data on the inher i tance patterns, re lat ing to exine

ornamentation and the germinal aperture (Ravikumar, 1979).

Some of the relevant works on the pol len morphology

pertaining to Polygalaceae family include those of Larson and Skvarla

(1961), Nair (1965), Simpson and Skvarla (1981) and Andrew (1984).

The present investigation has taken into consideration the modern

trends and approaches to study the pol len morphology including

morphological analyses with par t icu lar aim of taking stock o f

taxonomic and phylogenetic relationships of the taxa belonging to the

group.

The seed is a very important part of the plant, principally by

forming the l ink between successive generations (Bournan, 1978).

Morphology of seed coat is usually stable as it is little influenced by

external environmental conditions due to its development and ripening

within the fruit (Heywood, 1971). The seed morphological characters

like size, shape, caruncle, apex and surface ornamentation are stable

and reliable. Hence they furnish excellent characters for identification

and are taken into considerat ion for taxonomic treatment. Today,

scanning electron microscope has become one of the strongest tools

available for taxonomic research because of its potential to disclose

new dimensions of surface details (Heywood and Dakshini , 1971).

Seed biology has attracted the attent ion of b io logis ts not only

because of its significance in elucidating the evolutionary dynamics of

p lant populat ions, but a lso due to i ts appl icat ion in agricul ture,

forestry and horticulture (Stebbins, 1974 and Harper, 1977).

Ear l ier works on Polygalacean seeds include those of

Chodat (1 891). Rodrigue (1 893). Milby (1 976). Verkerke and Bouman

(1980), Verkerke (1984), Merlee Teresa (1986 , 1988) and Merlee

Teresa and Liza (1999). The structure and relationship of integument

and seed coat of some Polygala, Linn. species were studied by

Chodat (1 891) and Rodrigue (1 893). Verkerke and Bouman (1 980)

and Verkerke (1984) have analysed the ovule ontogeny and its

relation to seed coat structure of certain species of Polygala, Linn.

and Xanthophyllum, Roxb. Studies on seed dormancy and germination

pattern of eight Polygala, Linn. species were carried out by Merlee

Teresa (1986). Light microscopic observat ions of the strophiolar

variation in fourteen species of Polygala, Linn. were made by Merlee

Teresa (1988) and Merlee Teresa and Liza (1999).

The present work is an attempt to study the surface

microsculpture of seeds using scanning electron microscopy to reveal

even the minutest also to prove

the uniqueness of seeds. -, - -. ,,,

/ "" . ,' ,/ _ C _-

The embryology of angiosperms is a research area providing

investigations on all the events relevant to sexual reproduction.

Comparative embryology has been an important factor in revealing the

relationships of taxa at all levels (Herr, 1984). The embryological

features that have been applied in taxonomy by earlier workers are

manifold. They include basically all morphological characters

concerned with the development of anthers, ovules and seeds. Among

the various embryological characters, structure and development of

female gametophyte have the greatest potential value in taxonomic

considerations (Maheshwari, 1950). Embryological features are

especially significant in situations where exomorphology either leads to

inconclusive co-relations or may even delude due to convergence

(Kapi l and Bhatnagar, 1980). Studies on embryo and endosperm

development contribute invaluable information on testa1 histology and

its taxonomic significance (Carlquist, 1961 and Corner, 1976). The

bearing of embryological characters in our understanding of

angiosperm phylogeny has been reviewed by Palser (1975). The

potential role of embryology in taxonomy of flowering plants has been s

widely discussed by Maheshwari (1950 , 1963). Johri (1963) and

Kapil and Bhatnagar (1980). Davis (1966) has provided an excellent

treatise on the systematic embryology of angiosperms. In the present

investigation, one species each of Salomonia, DC., Polygala, Linn.

and Xanthophyllum, Roxb. were selected for systematic embryological

studies, so as to correlate with other characters in tracing out

interrelationships.

Thus within the limits of a thesis , the present work is an

attempt to analyse structural as well as chemical information about

foliar epidermis, embryological and morphological features of pollen

grains and seeds that represent vegetative and reproductive

parameters of selected members of the family Polygalaceae.

Controversy prevailing about the systematic position of Xanthophyllum,

Roxb. as revealed by the: l i terature survey and the unique floral \," -

characters of this family among the angiosperms have been the

subject of interest to select this family for the present exploration.

Apart from its taxonomic importance, some members of this family

have medicinal value . The present study is undertaken with the

following objectives:

(1) To analyse stomatal complex in the light of morphology and

histochemistry .

(2) To reveal the role of histochemistry in the systematics of the

family . 4

(3) To study the extent of variation in the distribution of

histochemical metabolites in the foliar epidermis.

(4) To record the observations on stornatal index, stomatal

frequency and palisade ratio.

(5) To analyse the observations on the external morphology of

pollen grains for taxonomic purposes.

(6) To prepare certain standards for the study of external

morphology of seeds.

(7) To record the diversity in the exomorphic features of the seeds

of different taxa.

(8) To study the reproductive characters and to reveal the role of

embryology in systematics.

(9) To detect the evolutionary trends responsible for the diversity

in the morphological and histochemical parameters.

(10) To stabilize the systematic position of the controversial and

interesting genus Xanthophyllum, Roxb.

11. MATERIALS AND METHODS