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Rangachari, K / A Handbook of Some South Indian Grasses
(This file was
produced from images generously made available by The
Internet Archive/Million Book Project)







A HANDBOOK
OF
SOME SOUTH INDIAN GRASSES


BY
RAI BAHADUR K. RANGA ACHARIYAR, M.A., L.T.,
_Indian Agricultural Service, Agricultural College, Coimbatore, and
Fellow of the Madras University_


ASSISTED BY
C. TADULINGA MUDALIYAR, F.L.S.,
_Agricultural College, Coimbatore._


MADRAS:
PRINTED BY THE SUPERINTENDENT, GOVERNMENT PRESS.
1921

Price, 4 _rupees_ 8 _annas_




PREFACE


This book is intended to serve as a guide to the study of grasses of the
plains of South India. For the past few years I have been receiving
grasses for identification, almost every week, from the officers of the
Agricultural and Forest Departments and others interested in grasses.
The requirements of these men and the absence of a suitable book induced
me to write this book.

I have included in this book about one hundred grasses of wide
distribution in the plains of South India. Many of them occur also in
other parts of India. The rarer grasses of the plains and those growing
on the hills are omitted, with a view to deal with them separately.

The value of grasses can be realized from the fact that man can supply
all his needs from them alone, and their importance in agriculture is
very great, as the welfare of the cattle is dependent upon grasses.
Farmers, as a rule, take no interest in them, although profitable
agriculture is impossible without grasses. Very few of them can give the
names of at least half a dozen grasses growing on their land. They
neglect grasses, because they are common and are found everywhere. They
cannot discriminate between them. To a farmer "grass is grass" and that
is all he cares to trouble himself about. About grasses Robinson writes
"Grass is King. It rules and governs the world. It is the very
foundation of all commerce: without it the earth would be a barren
waste, and cotton, gold, and commerce all dead."

In the early days when the population was very much limited and when
land not brought under cultivation was extensive plenty of green grasses
was upon it and pastures were numerous. So the farmer paid no attention
to the grasses, and it did not matter much. But now, population has
increased, unoccupied land has decreased very much and the cattle have
increased in number. Consequently he has to pay more attention to
grasses.

On account of the scarcity of fodder, people interested in agriculture
and cattle rearing have very often imported foreign grasses and fodder
plants into this country, but so far no one has succeeded in
establishing any one of them on any large scale. Usually a great amount
of labour and much money is spent in these attempts. If the same amount
of attention is bestowed on indigenous grasses, better results can be
obtained with less labour and money. There are many indigenous grasses
that will yield plenty of stuff, if they are given a chance to grow. The
present deterioration of grasses is mainly due to overgrazing and
trampling by men and cattle.

To prove the beneficial effects which result from preventing overgrazing
and trampling, Mr. G. R. Hilson, Deputy Director of Agriculture (now
Cotton Expert), selected some portion of the waste land in the
neighbourhood of the Farm at Hagari and closed it for men and cattle. As
a result of this measure, in two years, a number of grasses and other
plants were found growing on the enclosed area very well, and all of
them seeded well. Of course the unenclosed areas were bare as usual.

In the preparation of this book I received considerable help from
M.R.Ry. C. Tadulinga Mudaliyar Avargal, F.L.S., Assistant Lecturing and
Systematic Botanist, in the description of species and I am indebted to
M.R.Ry. P.S. Jivanna Rao, M.A., Teaching Assistant, for assistance in
proofreading.

I have to express my deep obligation to Mr. G. A. D. Stuart, I.C.S.,
Director of Agriculture, for encouragement to undertake this work and to
the Madras Government for ordering its publication.

For the excellence in the get up of the book I am indebted to Mr. F. L.
Gilbert, Superintendent, Government Press.

K. RANGACHARI.

AGRICULTURAL COLLEGE,
LAWLEY ROAD, COIMBATORE,
_2nd June 1921._




CONTENTS

PAGE
PREFACE iii
CHAPTER I--Introduction 1
II--The vegetative organs 5
III--The inflorescence and flower 13
IV--Histology of the vegetative organs 19
V--Classification 43
VI--Panicaceĉ 45
VII--Oryzeĉ and Zoysieĉ 123
VIII--Andropogoneĉ 138
IX--Agrostideĉ and Chlorideĉ 220
X--Festucaceĉ and Hordeĉ 283
GLOSSARY 311
INDEX 315




A HANDBOOK OF SOME COMMON SOUTH
INDIAN GRASSES.




CHAPTER I.

INTRODUCTION.


Grasses occupy wide tracts of land and they are evenly distributed in
all parts of the world. They occur in every soil, in all kinds of
situations and under all climatic conditions. In certain places grasses
form a leading feature of the flora. As grasses do not like shade, they
are not usually abundant within the forests either as regards the number
of individuals, or of species. But in open places they do very well and
sometimes whole tracts become grass-lands. Then a very great portion of
the actual vegetation would consist of grasses.

On account of their almost universal distribution and their great
economic value grasses are of great importance to man. And yet very few
people appreciate the worth of grasses. Although several families of
plants supply the wants of man, the grass family exceeds all the others
in the amount and the value of its products. The grasses growing in
pasture land and the cereals grown all over the world are of more value
to man and his domestic animals than all the other plants taken
together.

To the popular mind grasses are only herbaceous plants with narrow
leaves such as the hariali, ginger grass and the kolakattai grass. But
in the grass family or Gramineĉ the cereals, sugarcane and bamboos are
also included.

Grasses are rather interesting in that they are usually successful in
occupying large tracts of land to the exclusion of other plants. If we
take into consideration the number of individuals of any species of
grass, they will be found to out-number those of any species of any
other family. Even as regards the number of species this family ranks
fifth, the first four places being occupied respectively by Compositĉ,
Leguminosĉ, Orchideĉ and Rubiaceĉ.

As grasses form an exceedingly natural family it is very difficult for
beginners to readily distinguish them from one another.

The leaves and branches of grasses are very much alike and the flowers
are so small that they are liable to be passed by unnoticed. The
recognition of even our common grasses is quite a task for a botanist.

To understand the general structure of grasses and to become familiar
with them it is necessary to study closely some common grasses. We shall
begin our study by selecting as a type one of the species of the genus
Panicum.

_Panicum javanicum_ is an annual herb with stems radiating in all
directions from a centre. The plant is fixed to the soil by a tuft of
fibrous roots all springing from the bases of the stems. In addition to
this crown of fibrous roots, there may be roots at the nodes of some of
the prostrate branches. The stems and branches are short at first, and
leaves arise on them one after the other in rapid succession. After the
appearance of a fair number of leaves the stem elongates gradually and
it finally ends in an inflorescence.

[Illustration: Fig. 1.--Panicum javanicum. (Full plant.)]

The stem consists of =nodes= and =internodes=. The internodes are
cylindrical and somewhat flattened on the side towards the axillary bud.
When young they are completely covered by the leaves and the older ones
have only their lower portions covered by the leaf-sheaths. Usually they
complete their growth in length very soon, but the lower portion of the
internode, just above the node and enclosed by the sheath, retains its
power of growth for some time.

The leaf consists of the two parts, the =leaf-sheath= and the
=leaf-blade=. At the junction of these two parts there is a very thin
narrow membrane with fine hairs on its free margin. This is called the
=ligule=. (See fig. 2.)

The leaf-sheath is attached at its base to the node and it is slightly
swollen just above the place of insertion. It covers the internode, one
margin being inside and the other outside. The surface of the sheath is
sparsely covered with long hairs springing from small tubercles. The
outer margin of the sheath bears fine hairs all along its length. (See
fig. 2.)

The leaf-blade is broadly lanceolate, with a tip finely drawn out. Its
base is rounded and the margin wavy, especially so towards the base. On
the margin towards the base long hairs are seen, and some of these arise
from small tubercles. The margin has a hyaline border which is very
minutely serrate. There is a distinct midrib and, on holding the leaf
against the light, four or five small veins come in to view. In the
spaces between these veins lie many fine veins. All the veins run
parallel from the base to the apex. At the base of the blade the veins
get into the leaf-sheath and therefore the sheath becomes striated. Just
above the ligule and at the base of the leaf-blade there is a colourless
narrow zone. This is called the =collar=.

[Illustration: Fig. 2.--Leaf of Panicum javanicum.

A. Full leaf; B. a portion of the leaf showing 1. the ligule and 2. the
collar.]

As already stated the inflorescences appear at the free ends of
branches. Every branch sooner or later terminates in an inflorescence
which is a compound raceme. There are usually five or six racemes in the
inflorescence. Each raceme has an axis, called the =rachis=, which bears
unilaterally two rows of bud-like bodies. These bud-like bodies are the
units of the inflorescence and they are called =spikelets=. (See fig.
3.)

[Illustration: Fig. 3.--The inflorescence of Panicum javanicum.

1. Inflorescence; 2 and 3. the front and the back view of a raceme.]

The spikelets are softly hairy and are shortly stalked. The pedicels of
spikelets are hairy and sometimes one or two long hairs are also found
on them. Each of these spikelets consists of four green membranous
structures called =glumes=. The first two glumes are unequal, the first
being very small. The second and the third glumes are broadly
ovate-oblong with acute tips. Both are of the same height and texture,
but the second is 7-nerved and the third 5-nerved. The fourth glume is
membranous when young, but later on it becomes thick, coriaceous and
rugose at the surface. Just opposite to the fourth glume there is a flat
structure with two nerves, similar to the glume in texture. This is
called the =palea=. The fourth glume and its palea adhere together by
their margins. Inside the fourth glume and between it and the palea
there are three stamens and an ovary with two styles ending in feathery
stigmas. Just in front of the ovary and outside the stamens two very
small scale-like bodies are found. These are the =lodicules=. They are
fleshy and well developed in flowers that are about to open. In the
spikelet there is only one full flower. The third glume contains no
flower in it, but occasionally there may be in its axil three stamens.
The first two glumes are always empty and so they are called empty
glumes. (See fig. 4.) In mature spikelets the grain which is free is
enclosed by the fourth glume and its palea.

[Illustration: Fig. 4.--Parts of the spikelets of Panicum javanicum.

A. A spikelet; 1, 2, 3 and 4. the first, second, third and the fourth
glume, respectively; 3a. palea of the third glume; 4a. palea of the
fourth glume; 5. lodicules; 6. stamens; 7. ovary; 8. stigmas.]




CHAPTER II.

THE VEGETATIVE ORGANS.


Grasses vary very much in their habit. Some grasses grow erect forming
tufts and others form cushions with the branches creeping along the
ground. (See figs. 5 and 6.) We usually find all intermediate stages
from the erect to the prostrate habit. Underground stems such as stolons
and rhizomes occur in some grasses. Grasses of one particular species
generally retain the same habit but this does not always hold good. For
example _Tragus racemosus_ grows with all its branches quite prostrate
in a poor, dry, open soil. If, on the other hand, this happens to grow
in rich soils, or amidst other plants or grasses, it assumes an erect,
somewhat tufted habit. _Andropogon contortus_ and _Andropogon pertusus_
are other grasses with a tendency for variation in habit. Plants that
are usually small often attain large dimensions under favourable
conditions of growth. Ordinarily the grass _Panicum javanicum_ grows
only to 1 or 2 feet. (See fig. 1.) The same plant in a good rich soil
grew to about 6 feet in four months. (See fig. 7.)

[Illustration: Fig. 5.--Eleusine ĉgyptiaca.]

Some grasses are annual while others are perennial. It is often
difficult to determine whether a certain grass is annual or perennial.
But by examining the shoot-system this can be ascertained easily. In an
annual all the stems and branches usually end in inflorescences and they
will all be of the same year. If, on the other hand, both young leafy
branches and old branches ending in inflorescences are found mixed, it
must be a perennial grass. The presence of the remains of old leaves,
underground stolons and rhizomes is also evidence showing the perennial
character of the plant.

Grasses are eminently adapted to occupy completely large areas of land.
They are also capable of very rapid extension over large areas, on
account of the production of stolons, rhizomes and the formation of
adventitious roots.

=The root-system.=--The root-system of grasses is very striking in its
character. In most grasses, especially in erect ones, several roots all
of about the same diameter arise in a dense tuft from nearly the same
level and from the lower-most nodes of the stems. The roots are all thin
and fibrous in the vast majority of these plants, and they are tough and
wiry only in a few cases such as in the case of the roots of _Pennisetum
cenchroides_, _P. Alopecuros_, _Ischĉmum pilosum_ and _Andropogon
Schoenanthus_.

On a close examination it will become evident that all the roots of a
grass plant are adventitious. Inasmuch as the growth of the primary root
is soon overtaken by other roots growing from the stem, all the roots
happen to be of the same size. Roots arise from the nodes just above the
insertion of the leaf, and they grow piercing the leaf-sheath.

[Illustration: Fig. 6.--Panicum Crus-galli.]

Grasses in which stolons and prostrate branches occur have, in addition
to the usual radiating crown of roots at the base, aerial roots growing
out of the upper nodes of the branches and fixing them to the soil. Such
roots become supporting or prop roots and are particularly conspicuous
in several stout tall grasses such as _Andropogon Sorghum_, _Zea Mays_
and _Pennisetum typhoideum_. (See figs. 8 and 9.)

All the roots bear branch-roots which originate from the inner portion
of the mother roots in the usual manner. The character and the extent of
the development of the root-system is to a large extent dependent upon
the nature of the soil and its moisture content. In light dry soils
roots remain generally stunted and in well drained rich soils they
attain their maximum development. In clayey soils roots penetrate only
to short distances. When the soil is rich and sandy roots go deeper and
extend in all directions. The root-systems of most grasses are
superficial and so are best adapted for surface-feeding.

[Illustration: Fig. 7.--Panicum javanicum.]

=The shoot-system.=--The shoot-system varies with the duration of the
life of the plant. In annual grasses stems are in most cases erect and
even if they are not entirely so they become erect at the time of
flowering. They are attached to the soil by a tuft of fibrous roots
arising from the base of the stems. But in perennials in addition to
erect branches, creeping branches, stolons and rhizomes may occur.

[Illustration: Fig. 8.--Prop roots of Andropogon Sorghum.]

[Illustration: Fig. 9.--Aerial roots of Ischĉmum ciliare.]

The stem is either cylindrical or compressed and consists of nodes and
internodes. In most grasses the internodes are usually hollow, the
cavity being lined by the remains of the original pith cells. However,
there are also grasses in which the stems remain solid throughout. In
many grasses the basal portions of stems are more leafy and the
internodes are short, but in the upper portions the internodes become
longer separating the leaves one from the other.

In young shoots the leaves grow much faster than the internodes and
consequently internodes remain small, and leaves become very
conspicuous. The youngest portions of the shoots are by this means
always well protected by the surrounding leaf-sheaths. As soon as leaves
have grown fully, the internodes begin to elongate rapidly separating
the leaves. At first growth in length takes place throughout its length
in the internode and when it gets older this elongation ceases. But,
however, the lower portion of the internode close to the node and which
is enclosed by the leaf-sheath retains its power of growth for a
considerable time.

Branches arise from the axils of leaves and when a considerable number
of the axillary buds, especially from the lower nodes, develop into
branches the plant becomes tufted in habit. In most grasses branches
grow upwards through the sheath and emerge at its mouth as aerial
branches. Such branches are called =intravaginal= branches or stems. But
in some grasses axillary buds, instead of growing straight up through
the sheath, pierce the leaf-sheath, come out and then they grow out as
branches. This may be seen in the underground stolons of _Panicum
repens_ and in the ordinary aerial branches of _Arundo Donax_. Branches
that pierce through the sheaths are called =extravaginal= branches. (See
fig. 10.)

[Illustration: Fig. 10.--Extravaginal shoots of 1. Panicum repens and 2.
Arundo Donax.]

[Illustration: Fig. 11.--Nodes.

1. Glabrous node; 2. bearded node; 3. node cut longitudinally.]

The nodes are in most cases very conspicuous and they are often found
swollen. However, it must be remembered that the enlargement at the node
is not due to the increase in size of the actual node, but due to growth
in thickness of the base of the leaf-sheath. (See fig. 11-3.) Nodes may
be pale or coloured, glabrous, hairy or bearded with long hairs. When
the stem is erect the nodes are short and of uniform size all round.
But, if the stem is bent down or tipped over by accident, the nodes
begin to grow longer on the lower side until a curvature sufficient to
bring the stem to the erect position is formed and then it ceases to
grow.

As already noted some perennial grasses have creeping stems and stolons,
while others may have rhizomes. The grass _Cynodon dactylon_ develops
several underground stolons which are covered with white scale leaves
and whose terminal buds are hard and sharp so that they may be able to
make their way through the soil. The rhizomes when continuous and
elongated are usually sympodia formed by the lower portions of the
aerial shoots. The aerial shoot comes into the air and its lower portion
is continued by a branch arising from a lower leaf axil beneath the
soil.

=The leaf.=--Leaves are two-ranked and alternate, and very often they
become crowded at the lower portions of the shoots so as to form basal
tufts, though they are farther apart in the upper portions of these
shoots. Three distinct kinds of leaves are met with in grasses. First,
we have the fully formed foliage leaves so characteristic of grasses.
These are most conspicuous and are formed in large numbers.

The other two kinds of leaves are neither so conspicuous nor so numerous
as the foliage leaves. At the base of shoots occur abortive leaves which
are really rudimentary sheaths. These are called =scales=. The third
kind of leaf is a modified structure called the =prophyll= or
=prophyllum=. (See fig. 12.) It is the first leaf occurring in every
branch on the side next to the main shoot and it is a two-keeled
membranous structure resembling somewhat the palea found in the
spikelets of grasses. The portion of the prophyll between the keels is
concave due to the pressure of the main stem, while the sides beyond the
keels bend forward clasping the stem.

[Illustration: Fig. 12.--Prophylla.

A. A branch with its prophyllum; B. prophyllum; C. section of the
prophyllum.]

The ordinary foliage leaves of grasses consist of the two parts, the
flat expanded upper portion called the =blade= and the lower part called
the =sheath= that encircles the stem above the node from which it
arises. The leaf-sheaths usually fit close to the stem, but they may
also be loose or even inflated. Though the leaf-sheath surrounds the
internode like a tube, it is not a closed tube. It is really a flat
structure rolled firmly round the stem with one edge overlapping the
other. In most cases it is cylindrical and it may be compressed in a few
cases. Occasionally it may have a prominent ridge or keel down its back.
The sheath may be glabrous or hairy, smooth or striate externally, and
the outer margin is often ciliate. In a few grasses the sheaths become
coloured especially below or on the side exposed to the sun.

[Illustration: Fig. 13.--Ligules of 1. Oryza sativa; 2. Panicum
javanicum; 3. Andropogon Schoenanthus; 4. A. contortus.]

[Illustration: Fig. 14.--Shapes of leaf-blades.

1, 7 and 8. Lanceolate; 3 and 6. lanceolate-linear; 2 and 5. linear; and
4. ovate.]

The =ligule= is a structure peculiar to grasses and it varies very much.
In some grasses it is a distinct membrane narrow or broad, with an even,
truncate or erose margin, or finely ciliate. Very often it is only a
line or fringe of hairs, whilst in some it may be entirely absent as in
the leaves of _Panicum colonum_. When it is a membrane it may be broad
and oblong, ovate and obtuse, or lanceolate and acute. (See fig. 13.)
The function of the ligule is probably to facilitate the shedding of
water which may run down the leaf, and thus lessen the danger of rotting
of the stem which is sure to follow, if the water were to find its way
into the interior of the sheath. Sometimes, in addition to the ligule,
other appendages may be present in grass leaves as in _Oryza sativa_.
Such outgrowths are called =auricles= or =auricular outgrowths=. (See
fig. 13.)

The leaf-blade is well developed in the foliage leaves and in most cases
it follows directly on the sheath. But in bamboos and some species of
Ischĉmum there occurs a short petiole or stalk between the leaf-blade
and the sheath. The sheath corresponds morphologically to the leaf base
of a leaf of other flowering plants.

[Illustration: Fig. 15.--Margins of leaves.

1 and 2. Finely serrate; 3. glandular; 4 and 5. very minutely serrate;
6. very minutely serrate and ciliate.]

In grasses the leaf-blades usually grow more in length than in any other
direction and there is no limit to the length they may attain. Some
grasses have very short leaves, others very long ones. The leaf-blade in
most grasses is more or less of some elongated form, such as linear,
linear-lanceolate, lanceolate, etc. (See fig. 14.) In a few grasses the
leaf-blade is ovate, but this is a rare condition. Therefore, in noting
the general shape of the leaf-blade the relation of the length to the
breadth, the amount of tapering towards the apex and base and the nature
of the apex should be considered.

The veins in the leaf-blade can usually be seen on holding the leaf up
to the light. All the veins run parallel. In most cases the midrib is
prominent and in some cases there may be also a distinct keel. Amongst
the veins running through the leaf-blade some are large and prominent,
while others are small and not conspicuous. On account of this
disparity, very often, ridges and furrows become prominent on the upper
or lower, or on both the surfaces of the leaf-blades. Generally the two
surfaces of the leaf-blade are distinct, and they may be glabrous or
hairy. In most grasses the surfaces are rough or scabrid to the touch
owing to the presence of regular rows of exceedingly fine sharp pointed
minute hairs.

The apex of the blade is generally sharp and pointed, acute or
acuminate, or sometimes it may be drawn to a very fine point by gradual
tapering. Blunt or obtuse tips are not altogether absent, but it is not
a common feature. The leaf-blades in _Panicum colonum_ and in some
species of Andropogon are rounded or obtuse at the apex.

The margins of the leaf-blade are somewhat hyaline and they may be
perfectly even or cut into serrations of fine teeth in various ways.
(See fig. 15.) In addition to these minute teeth, there may be long or
short cilia. Sometimes the margins are glandular as in _Eragrostis
Willdenoviana_ and _Eragrostis major_.

The base of the leaf may be narrower, broader than, or about the same as
the breadth of the leaf-sheath. It may be rounded, amplexicaul or
narrowed. At the base and just above the ligular region there will
always be a white distinct zone in the lamina of all grasses called the
collar. This collar varies in length and breadth according to the
species of grass.

[Illustration: Fig. 16.--Transverse section of leaf-buds.

A. Conduplicate; 1, 2 and 3. leaf-sheaths; 4 and 5. leaf-blades. B.
Convolute; 1 and 2, leaf-sheaths; 3 and 4. leaf-blades.]

In young shoots all the leaf-blades are usually found folded at the
terminal portions. In most cases the leaf-blade is rolled up inwards
from one end to the other so that one margin is inside and the other
outside. This folding is termed =convolute=. This is the kind of folding
that is found in most grasses. However, there are some grasses such as
_Eleusine ĉgyptiaca_ and _Chloris barbata_, in which the folding is
different. In these grasses the laminas are folded flat on their midribs
so that each half of the blade is folded flat on the other, the inner
surfaces being in contact. The leaves are said to be =conduplicate= in
this case. When the leaves are conduplicate the shoots are more or less
compressed. (See fig. 16.)




CHAPTER III.

THE INFLORESCENCE AND FLOWER.


The flowers of grasses are reduced to their essential organs, the
stamens and the pistil. The flowers are aggregated together on distinct
shoots constituting the inflorescence of grasses. Sooner or later all
the branches of a grass-plant terminate in inflorescences which usually
stand far above the foliage leaves. As in other flowering plants, in
grasses also different forms of inflorescence are met with. But in
grasses the unit of the inflorescence is the =spikelet= and not the
flower.

The forms of inflorescence usually met with are the spike, raceme and
panicle. When the spikelets are sessile or borne directly along an
elongated axis as in _Enteropogon melicoides_ the inflorescence is a
=spike=. If the spikelets borne by the axis are all stalked, however
short the pedicels may be, it is a =raceme=. It must, however, be
remembered that true spikes are very rare. An inflorescence may appear
to be a spike, but on a close examination it will be seen to consist of
spikelets more or less pedicelled. Such an inflorescence, strictly
speaking, is a =spiciform raceme=. The branches of the inflorescence in
_Paspalum scrobiculatum_ or _Panicum javanicum_ are racemes and the
whole inflorescence is a compound raceme. The inflorescence is a
=panicle= when the spikelets are borne on secondary, tertiary or further
subdivided branches. Panicles differ very much in appearance according
to the relative length and stoutness of the branches. In _Eragrostis
tremula_ the panicle is very diffuse, in _Eragrostis Willdenoviana_ less
so. The panicle in _Sporobolus coromandelianus_ is pyramidal and the
branches are all verticillate, the lower being longer than the upper.
The branches of a panicle are usually loose, spreading or drooping in
most grasses. But in some species of grasses such as _Pennisetum
Alopecuros_ and _Setaria glauca_, the paniculate inflorescences become
so contracted that the pedicels and the short branches are hidden and
the inflorescence appears to be a spike. Such inflorescences as these
are called =spiciform panicles=. The inflorescences in several species
of Andropogon consist of racemes so much modified as to appear exactly
like a spike. What looks like a spike in these cases consists of a
jointed axis and each joint bears a pair of spikelets, one sessile and
the other pedicelled.

The name =rachis= is given to the axis of the spike, raceme and panicle,
whether the axis is the main one or of the branch. The rachis of the
inflorescence is usually cylindrical. In some grasses it is zigzag as in
_Pennisetum cenchroides_. It is very much flattened in _Paspalum
scrobiculatum_, but somewhat trigonous in _Digitaria sanguinalis_. In
very many grasses the rachis is continuous, but in a few cases it
consists of internodes or joints which disarticulate at maturity. Many
species of Andropogon have such jointed rachises. Sometimes the joints
become greatly thickened and the surface hollowed out, the spikelets
fitting in the cavities as in Rottboellia and Manisuris.

In panicles, especially when they are diffuse, the primary branches may
be disposed irregularly or in verticils on the main axis. For example in
the panicle of _Eragrostis Willdenoviana_, the branches are irregularly
disposed, whereas in _Sporobolus coromandelianus_ the branches are
verticillate. In both these grasses fleshy cushions are developed in the
axils of the branches. These swellings help to spread out the branches
especially at the time of anthesis. The branches at the top spread out
earlier than those below.

Sometimes at the base of the rachises, main or secondary, glandular
streaks are seen as in the rachises of _Sporobolus coromandelianus_.
These glands secrete a viscid juice at the time of anthesis.

[Illustration: Fig. 17.--The Spikelet of Dinebra arabica.

1 and 2. Empty glumes; 3, 4, 5, and 6. flowering glumes with flowers.]

The =spikelet= may be considered as a specialised branch consisting of a
short axis, the =rachilla= bearing a series of modified bracts, the
=glumes=, the lower pair being empty but the others bearing flowers in
their axils. The glumes are two-ranked and imbricating. As a type for
the spikelet that of an Eragrostis or Dinebra may be chosen. (See fig.
17.) In this spikelet the rachilla bears a number of glumes alternating
and imbricating. The first two glumes at the base of the spikelet do not
bear any flowers and so these two glumes are usually called empty
glumes. This is the case in almost all the species of grasses. The third
and the subsequent glumes are regularly arranged on the slender rachilla
alternately in two rows. In the axils of each of these glumes there is a
flower, except perhaps in the topmost glume. The flower is usually
enclosed by the glume and another structure found opposite the glume and
differing very much from the glume. This is the =palea=. It is attached
to the axis of the flower and its back is towards the rachilla.
Generally there are two nerves in a palea and its margins are enclosed
within those of the glume. The palea is homologous with the prophyllum
which it very much resembles. The prophyllum is usually found in the
branches of grasses, but it is not confined to grasses alone. It occurs
in the branches of some species of Commelina.

The spikelets vary very much in their structure. The spikelets in
grasses of several genera consist of only four glumes. As usual the
first two glumes are empty and the remaining two are flower-bearing
glumes. Both these glumes may have perfect flowers as in Isachne or the
terminal one may contain a perfect flower, the lower having either a
staminate flower or only a palea. Very often the spikelets are unisexual
and the male and female spikelets may be on the same plant as in _Coix
Lachryma-Jobi_ and _Polytoca barbata_, or they may be on different
plants as in _Spinifex squarrosus_.

The glumes of a spikelet are really modified bracts and some
differentiate the flowering glumes from the empty ones, by giving them
different names. The first two empty glumes are called glumes by all
agrostologists. Some in Europe call the flowering glume lower palea to
distinguish it from the real palea which they call the upper palea. Some
American Authors have recently adopted for the flowering glume the term
=lemma= introduced by Piper.

Considerable variation is met with in the case of the empty glumes.
Generally they are unequal, the first being smaller. Very often the
first glume becomes very small and it may be altogether absent. In some
species of Panicum the first glume is very small, in Digitaria it is
very minute and in Paspalum and Eriochloa it is entirely suppressed. The
flowering glumes are generally uniform when there are many. In the
spikelet having only four glumes the fourth glume differs from the
others mainly in texture. Instead of being thin and herbaceous it
becomes rigid and hard, smooth or rugose externally as in Panicum.
Flowering glumes instead of being like empty glumes, become very thin,
shorter and hyaline in Andropogon. Sometimes the flowering glumes are
awned. All of them may be awned as in Chloris or only the fourth glume
as in Andropogon.

The palea is fairly uniform in its structure in many grasses, but it is
also subject to variation. It becomes shorter in some and is absent in
others. Instead of having two nerves, it may have one and rarely more
than two. The palea can easily be distinguished from the glume, because
its insertion in the spikelet is different from that of the glume.

[Illustration: Fig. 18.--Flower of Chloris.

1. lodicules; 2. stamens; 3. ovary.]

The =lodicules= are small organs and they are the vestiges of the
perianth. In most grasses there are only two, but in Ochlandra and other
bamboos we meet with three lodicules. There are also some species with
many lodicules. In shape they are mostly of some form referable to the
cuneate form. They are of somewhat elongated form in Aristida and
Chloris. The function of the lodicules seems to be to separate the glume
and its palea so as to enable the stamens to come out and hang freely at
the time of anthesis. So it is only at the time of the opening of the
flowers that the lodicules are at their best. Then they are fairly
large, fleshy and thick and conspicuous. In the bud stage they are
usually small and after the opening of the flower they shrivel up and
are inconspicuous. There are also species of grasses in which the
lodicules are not found.

The =stamens= are three in number in the majority of grasses and six are
met with in Leersia, Hygrorhiza and Bamboos. Each stamen consists of a
very delicate long filament and an anther basifixed to the filament. But
as the anthers are long and the connective is reduced to its minimum,
they appear as if versatile when the stamens are out. When there are
three stamens one stands in front of the flowering glumes and the other
two in front of the palea, one opposite each edge of the palea. The
relative positions of the parts of the floret are shown in the floral
diagrams. (See figs. 18 and 19.)

[Illustration: Fig. 19.--Floral diagrams.

The first is that of Chloris, second of Panicum and the third of Oryza.]

The =pistil= consists of an ovary and two styles ending in plumose
stigmas. The ovary is 1-celled and 1-ovuled. It is one carpelled
according to the views of Hackel and his followers and there are also
some who consider it as 3-carpelled because of the occurrence of three
styles in the pistil of some bamboos.

The =rachilla= is usually well developed and elongated in many-flowered
spikelets, while in 1-flowered spikelets it remains very small so that
the flower appears to be terminal. It often extends beyond the insertion
of the terminal flower and its glume, and then lies hidden appressed to
the palea. This may be seen in the spikelets of the species of Cynodon.
This prolonged rachilla sometimes bears a minute glume, which is of
course rudimentary. Usually the glumes are rather close together on the
rachilla so that the internodes are very short; but in some grasses, as
in _Dinebra arabica_, the glumes are rather distant and so the
internodes are somewhat longer and conspicuous. In some species of
Panicum the rachilla is jointed to the pedicel below the empty glumes,
whereas it is articulated just above these glumes in _Chloris barbata_.
Sometimes the rachilla is articulated between the flowers. This is the
case in the spikelet of _Dinebra arabica_.

Pollination in most grasses is brought about by wind, though in a few
cases self-pollination occurs. The terminal position of the
inflorescence, its protrusion far above the level of the foliage leaves,
the swinging and dangling anthers, the abundance of non-sticking pollen
and the plumose stigmas are all intended to facilitate pollination by
wind. Furthermore the stamens and the stigmas do not mature at the same
time. In some grasses the stamens mature earlier, (=protandry=) while in
others the stigmas protrude long before the stamens (=protogyny=). As
the result of the pollination the ovary developes into a dry 1-seeded
indehiscent fruit. The seed fills the cavity fully and the pericarp
fuses with the seed-coat and so they are inseparable. Such a fruit is
termed a =caryopsis= or =grain=. Though in the vast majority of grasses
the pericarp is inseparable, in a few cases it is free from the
seed-coat as in _Sporobolus indicus_ and _Eleusine indica_.

[Illustration: Fig. 20.--Longitudinal section of a portion of the grain
of Andropogon Sorghum. × 280 P. Pericarp; Sc. seed-coat; A. aleurone
layer; E. endosperm; S. scutellum; Rs. root-sheath; Rc. root-cap; R.
radicle; Pl. plumule; G. growing point.]

[Illustration: Fig. 21.--A portion of the section of the grain of
Andropogon Sorghum. × 500 P. pericarp; I. seed-coat; A. aleurone layer;
S. starch.]

The caryopsis consists of an embryo on one side at the base and the
endosperm occupies the remaining portion. The embryo can be made out on
the side of the grain facing the glume, as it is outlined as an oval
area. On the other face of the grain which is towards the palea, the
hilum is seen at the base. The grain varies in shape considerably. It
may be rounded, oval, ellipsoidal, narrow and cylindrical, oblong terete
or furrowed. There is considerable variation as regards the colour also.

The =embryo= consists of an =axis= and a =scutellum=. The axis, which is
differentiated into the plumule directed upward and the radicle
downward, is small and straight and it is covered more or less by the
edges of the scutellum. The scutellum is attached to the axis at about
its middle and its outer surface is in contact with the endosperm. This
is an important organ as its function is to absorb nourishment from the
endosperm during germination. The scutellum is considered to represent
the first leaf or cotyledon. The endosperm consists mostly of starch.
Just outside the endosperm and within the epidermis lies a layer of
cells containing much proteid substance. This layer is called the
=aleurone layer=. (See fig. 21.) As an illustration of the caryopsis,
the grain of Andropogon Sorghum may be studied. All the structural
details are shown in fig. 20 which is a longitudinal section of the
grain.

The primary axis of the embryo is enclosed by a closed sheath both above
and below.



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