Distribution.—Plains of India and Ceylon and in all hot countries.
4. Panicum, L.
The grasses of this genus are annual or perennial and of various habits. Inflorescence is either a raceme of spikes or, a lax or contracted panicle. Spikelets are small, solitary or two to four, rarely more ranked, 1- to 2-flowered, ovoid or oblong, rounded, or dorsally or laterally compressed, falling entire with the pedicels. There are four glumes in a spikelet. The first two glumes are empty and the first glume is small (sometimes minute) and fewest nerved. The second glume is equal or very nearly equal to the third glume, oblong-ovate or lanceolate, 5- to many-nerved. The third glume is similar to the second, male or neuter, paleate or not, 3- to 9-nerved. The fourth glume is chartaceous, sometimes shortly stalked, ovate-oblong or lanceolate, hardened in the fruit, smooth or rough, bisexual, paleate; the palea is as long and of the same texture as the glume. Lodicules are cuneate or quadrate and two in number. There are three stamens and an ovary with two style branches ending in feathery stigmas. Grain is free and enclosed by the hardened fourth glume and its palea.
KEY TO THE SPECIES.
- A. Inflorescence racemose of simple (rarely branched) spikes bearing secund spikelets.
- I. Rachis of spikes broad and flattened.
- (a) Spikelets biseriate.
- Spikelets villous. 1. P. Isachne.
- Spikelets glabrous.
- (b) Spikelets 3- to 5-seriate.
- Third glume awned.
- Third glume cuspidate.
- (a) Spikelets biseriate.
- II. Rachis of spikes narrow, filiform, terete or angular.
- First glume shorter than the third.
- First glume semilunate, about 1/4 of the third glume. 7. P. prostratum.
- First glume 1/2 of or less than 1/2 of third glume, 5-nerved. 8. P. ramosum.
- Leaf base broad or cordate.
- Fourth glume shortly awned. 9. P. javanicum.
- Fourth glume muticous. 10. P. distachyum.
- First glume shorter than the third.
- I. Rachis of spikes broad and flattened.
- B. Inflorescence a contracted or open panicle.
- I. Panicle contracted and spike-like.
- Spikelets lanceolate and first glume minute. 11. P. interruptum.
- II. Panicle effuse.
- Annuals; first glume nearly 3/4 of the third glume. 12. P. trypheron.
- Perennials; first glume less than 1/3 of the third glume. 13. P. repens.
- I. Panicle contracted and spike-like.
Fig. 80.—Panicum Isachne.