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.

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 Gramineæ 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 Compositæ, Leguminosæ, Orchideæ and Rubiaceæ.

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.

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.

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.)

Fig. 3.—The inflorescence of Panicum javanicum.
1. Inflorescence; 2 and 3. the front and the back view of a raceme.

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.

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.)

Fig. 5.—Eleusine ægyptiaca.

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.

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.)

Fig. 7.—Panicum javanicum.

Fig. 8.—Prop roots of Andropogon Sorghum.

Fig. 9.—Aerial roots of Ischæmum 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.

Fig. 10.—Extravaginal shoots of 1. Panicum repens and 2. Arundo Donax.

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.

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.

Fig. 13.—Ligules of 1. Oryza sativa; 2. Panicum javanicum; 3. Andropogon Schœnanthus; 4. A. contortus.

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 Ischæmum 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.

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.

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 ægyptiaca 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.)

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.

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.

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.

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.