The spikelets are 1- to 2-flowered in dissimilar pairs, one globose, sessile and bisexual and the other ovate, pedicelled, neuter; the pedicel is adnate to the joint of the rachis.
The sessile spikelet has four glumes. The first glume is hard, globose, foveolate, with an oblong opening, faintly nerved. The second glume is chartaceous, immersed in the cavity of the joint, and filling the opening. The third glume is small hyaline and empty. The fourth glume is hyaline, small and paleate. The grain is sub-globose. Lodicules are broadly cuneate.
The pedicelled spikelets also have four glumes. The first glume is ovate, sub-chartaceous, winged on one side with a broad hyaline ciliate wing, 5- to 7-veined. The second glume is cymbiform, compressed laterally, with a dorsal hyaline ciliate wing to the keel, 5- to 7-veined. The third glume is hyaline, membranous, oblong, 2-nerved and paleate or not, and with or without stamens. The fourth glume is similar to the third, but slightly smaller, paleate and with three stamens.
This grass occurs in open loamy soils and in cultivated dry fields.
Distribution.—Throughout India and Ceylon and also in most of the tropical countries.
28. Andropogon, L.
The grasses of this genus are either perennial or annual and vary very much in habit. The inflorescence consists of solitary, binate, digitate, or panicled racemes. The rachis is usually jointed and fragile. Spikelets are binate, a sessile female or bisexual and a pedicelled male or neuter. The sessile spikelet is 1-flowered and has usually four glumes. The first glume is coriaceous or chartaceous, dorsally compressed, with incurved margins, usually 2-keeled. The second glume is as long as the first, thinner, with a median keel, laterally compressed, awned or not. The third glume is hyaline, empty, nerveless and without a palea. The fourth glume is hyaline, narrow or broad, 2-fid and awned, or reduced to an awn more or less dilated at the base, paleate or not. There are two lodicules and three stamens. Stigmas are feathery. Grain is free. The pedicelled spikelets are usually smaller than the sessile and have three or four glumes and are awnless.
KEY TO THE SPECIES.
- A. Sessile spikelets all similar.
- B. Racemes of many spikelets.
- C. Peduncle of racemes enclosed in spathiform leaf-sheaths.
- D. Joints of rachis and pedicels of upper spikelets slender and tips obliquely truncate.
- DD. Joints of rachis and pedicels of upper spikelets clavate or trumpet-shaped and tips cupular with toothed margins.
- CC. Peduncle of racemes not enclosed in spathiform leaf-sheath.
- Racemes many, fascicled or panicled, glume I of sessile spikelets glabrous and pitted. 3. A. pertusus.
- Racemes many and whorled in the panicle; glume I of sessile spikelets muricate on the margins. 4. A. squarrosus.
- C. Peduncle of racemes enclosed in spathiform leaf-sheaths.
- BB. Racemes of 3 spikelets on the capillary whorled branches of an erect panicle.
- B. Racemes of many spikelets.
- AA. The lowest one or more sessile spikelets in all racemes, or
at least in one or two, differing from all those above.
- Racemes digitate, rarely solitary, spikelets all alike in form
but differing in sex.
- Pedicel 1/3 as long as the sessile spikelets; nodes usually glabrous; ligule usually short and membranous. 8. A. caricosus.
- Pedicel 1/2 as long as the sessile spikelets; nodes bearded; ligule large and membranous. 9. A. annulatus.
- Racemes solitary; lower sessile spikelets very unlike the
pedicelled or upper spikelets which are cylindric.
- Margin of glume 1 of the pedicelled spikelet unequally winged; ligule is a broad truncate membrane. 10. A. contortus.
- Racemes two, both sessile, or one sessile and the other pedicelled
on a peduncle which is more or less sheathed
by a proper spathe, divaricate or deflexed.
- Leaf base broad and cordate 11. A. Schœnanthus.
- Racemes digitate, rarely solitary, spikelets all alike in form
but differing in sex.