A Handbook Of Some South Indian Grasses Part 6

The first glume of the spikelet is the smallest. In Panic.u.m it is nearly two-thirds or less than the third glume. It is very small in Digitaria and entirely suppressed in Paspalum. In Eriochloa it is reduced to a minute ridge lying just close to the swollen ring-like joint of the rachilla. The second and the third glumes are more or less equal and similar in texture. The fourth glume becomes firm and rigid along with its palea and usually encloses the grain.

The pedicel is jointed in some genera and in others it is continuous with the spikelet and not jointed. When mature the spikelets fall away either by themselves, singly with their pedicels or in groups with portions of rachis, according to the position of the joint. Bristles (branchlets) are often found on the pedicels. In Setaria a few are borne by the pedicels. The bristles form a regular involucre at the base of a group of spikelets in Pennisetum, and in Cenchrus these become united at the base into a ma.s.s forming a kind of burr around the spikelets.

KEY TO THE GENERA.

A. Spikelets articulate on their pedicels.

B. Spikelets without involucels.

C. Spikelets dorsally flattened, awnless.

Inflorescence racemed; glumes three; nerves of second glume five or less, side nerves curved 1. Paspalum.

Inflorescence digitate; glumes three with a minute glume; nerves of second glume five to seven, straight and prominent 2. Digitaria.

Inflorescence panicled; glumes three with a thickening at the base of the spikelet 3. Eriochloa.

Inflorescence racemed or paniculate; glumes four, first two glumes unequal 4. Panic.u.m.

Inflorescence panicled, branches of panicle produced beyond the uppermost spikelet; glumes four, the first being minute and hyaline 5. Chamaeraphis.

Spikelets unis.e.xual and dioecious 6. Spinifex.

CC. Spikelets awned.

Glumes four, second glume broadly fimbriate with hairs; palea of the third glume short and deeply cleft, fourth glume awned 7. Axonopus.

BB. Spikelets involucellate 8. Setaria.

AA. Spikelets not jointed but continuous.

Spikelets in involucelled deciduous fascicles.

Involucre of bristles free 9. Pennisetum.

Involucre of bristles united 10. Cenchrus.

1. Paspalum, _L._

These are annuals or perennials. The spikelets are plano-convex, orbicular to oblong, obtuse, secund, 2-ranked on the flattened or triquetrous rachis of the spike-like branches of a raceme, one-flowered and falling off entire from the very short or obscure pedicels. There are three glumes, all more or less equal and similar. The first and the second glumes are membranous, alike and as long as the third, the second glume is usually epaleate and occasionally with a minute palea. The third glume is chartaceous to sub-coriaceous and paleate. Lodicules are two and small. Stamens are three. The styles are slender and distinct with plumose stigmas exserted at the top of the spikelet. Grain is tightly enclosed in the third glume and its palea.

[Ill.u.s.tration: Fig. 69.--Paspalum scrobiculatum.]

=Paspalum scrobiculatum, _L._=

This is an annual gra.s.s, with stems tufted on very short rhizomes, erect or very shortly bent at base, glabrous, bifariously leafy and varying in height from 1 to 3 feet or more.

_Leaf-sheaths_ are compressed, glabrous, loose, keeled, mouth hairy or not. The _ligule_ is a short thin membrane. The _nodes_ are glabrous.

The _leaf-blade_ is linear-lanceolate, finely ac.u.minate, keeled with a distinct midrib, and with very minutely serrulate margins, 6 to 18 inches by 1/12 to 1/3 inch.

The _inflorescence_ consists of 2 to 5 sessile alternate spikes, usually distant and spreading and varying in length from 1 to 8 inches; the rachis is flattened and winged.

The _spikelets_ are either orbicular or ovate-oblong, as broad as the rachis, glabrous, closely imbricating in two rows (rarely in three or four rows), sessile or rarely geminate on a common pedicel.

There are three glumes. The _first glume_ is concave, 3- to 5-nerved (rarely 3- to 7-nerved). The _second glume_ is flat, 5-nerved, with two strong sub-marginal nerves, sometimes with shallow transverse pits along the margins. The _third glume_ is thickly coriaceous, brownish, shining, minutely striolate, margins roundly incurved throughout its length, paleate; the _palea_ is similar to the glume in structure and colour, margins strongly inflexed and with two broad membranous auricles almost overlapping just below the middle. There are three _stamens_. The _stigmas_ are white both when young and while fading. The style branches are diverging widely and then straight. There are two oblong cuneate fleshy _lodicules_.

[Ill.u.s.tration: Fig. 70.--Paspalum scrobiculatum.

1 and 2. Front and back view of a portion of spike; 3, 4 and 5.

spikelets; 6, 7 and 8. the first, second, and the third glume, respectively; 9. palea of the third glume; 10. the ovary, stamens and the lodicules.]

This gra.s.s flourishes all over the Presidency in moist places, such as, bunds of wet lands, edges of ponds and lakes and in marshy land. There are two forms of this gra.s.s, one with round and another with ovate oblong spikelets. They also vary in the size of the spikelets--some forms have small spikelets and others large. Sometimes the spikelets show variation in the number of glumes.

This gra.s.s is also cultivated for its grain. In cultivated forms the spikelets are larger and the whole plant grows bigger. It is grown both in wet and dry land.

_Distribution._--Throughout India (wild and also cultivated).

2. Digitaria, _Rich._

Annuals or perennials. The spikelets are lanceolate, 2- to 3-nate, in digitate or racemose spikes, jointed on the pedicels but not thickened at the base, 1-flowered. There are usually four dissimilar glumes in the spikelet. The first glume is hyaline very minute, sometimes absent in the same species. The second glume is membranous, 1- to 5-nerved or nerveless. The third glume is membranous, almost equal to the fourth, usually 7- to 9-nerved, the nerves being straight, close, parallel and prominent, with a minute palea or without a palea. The fourth glume is chartaceous or sub-chartaceous, usually 3-nerved and paleate; palea is equal to and similar to the fourth glume, 2-nerved. Lodicules are two, small, broadly cuneate. Stamens are three. Styles are distinct with plumose stigmas exserted laterally near the apex of the spikelet. Grain is enclosed in the fourth glume and its palea.

KEY TO THE SPECIES.

Spikelets 1/10 inch or more.

Spikes usually few, spikelets bearded 1. D. sanguinalis. Var. ciliaris.

Spikelets not bearded 2. Do. Var. extensum.

Spikes usually many; spikelets spreading 3. Do. Var. Griffithii.

Spikelets less than 1/10 inch.

Spikes narrowly winged; spikelets subsilky with slender (not clavellate) hairs 4. D. longiflora.

[Ill.u.s.tration: Fig. 71.--Digitaria sanguinalis, _Var. ciliaris_.]

=Digitaria sanguinalis, _Scop._=

_Var. ciliaris._