110 A FLORA OF MANILA 
4. Rachis glabrous. 
5. Leaves very short, less than 5 cm long; spikelets crowded. 
8. C. malaccensis 
5. Leaves long, sometimes equaling the stem; spikelets laxly 
disposed.:.-4.;.--0si-e 0oe-tb cand et ee ae 9. C. distans 
2. Rachilla of spikelets distinctly winged. 
3. Slender plants less than 0.5 m high. 
4, Spikes mostly dense, of from 3 to 8 spikelets; roots with thickened, 
ovoid or giobose tubers. 10. C. rotundus 
4. Spikes lax, of from 2 to 6 spikelets; glumes rather distant. 
11. C. zollingeri 
3. Coarse plants often 1 m high;'spikes 3 to 6 at the end of each 
branch of the inflorescence, densely many-flowered. 
12. C. radiatus 
1. C. difformis L. 
A tufted glabrous annual 10 to 40 cm long, the stems sharply 3-angled at 
the top. Leaves rather flaccid, somewhat shorter than the stems, 2 to 3 
mm wide. Inflorescence umbellate, simple or compound, subtended by two 
leaf-like bracts, contracted or spreading, the rays 1 to 5 em long, some 
sessile, some long-peduncled. Spikelets very numerous, 2 to 5 mm long, 
crowded in globose or ovoid masses on the ends of the branches, each 
spikelet with from 8 to 25 flowers, the flowering glumes about 0.6 mm 
long, obtuse, brownish. Nutlets about 0.6 mm long. 
In open wet grass lands, fl. all the year; throughout the Philippines. A 
characteristic rice-paddy weed throughout the warmer parts of the Old 
World, introduced in Mexico. 
2. C. haspan L. 
A tufted, glabrous, rather flaccid plant 10 to 40 cm high. Leaves often 
as long as the stem, sometimes shorter, or nearly wanting, 3 to 5 mm wide. 
Inflorescence umbellate, simple or compound, of few or many crowded or 
spreading rays, each with few to many spikelets, dense or lax. Spikelets 
brown, 3 to 10 mm long, 8- to 25-fiowered, the glumes about 1.2 mm long, 
imbricate, obtuse. Nutlets 3-angled, about 0.4 mm long. : 
In open, wet, grass lands, especially rice-paddies, fi. all the year; through- 
out the Philippines. All warm countries; a characteristic rice-paddy weed. 
*3. C. FLABELLIFORMIS Rottb. Umbrella Plant. 
A stout, erect, tufted plant reaching a height of 1.5 m, the stems up to 
1 cm in diameter, base covered with leafless sheaths. Leaves all crowded 
in a dense, spirally arranged whorl at the ends of the stems, spreading, nu- 
merous, up to 30 cm long, 0.5 to 2 cm wide, acuminate. Umbels in the 
leaf-axils, numerous, 8 cm wide or less, their peduncles slender, 10 cm long 
or less. Spikelets sessile, in peduncled and sessile heads, oblong, up to 1 
cm long, the glumes 20 to 30, about 2 mm long. Nuts 0.8 mm long. 
Frequently cultivated, but not spontaneous, fl. Dec—March. A native of 
Arabia and Abyssinia, now cultivated in many warm countries. 
4. C. diffusus Vahl. 
An erect glabrous perennial 30 to 60 cm high, the leaves basal, flat, 
broad, numerous, crowded, equaling or longer than the stems, 3-nerved, 8 
to 15 mm wide, the root-stock short. Stems 3-angled, the bracts subtend- 
ing the inflorescence leaf-like, 10 to 50 cm long, broad, spreading. Umbels 
8 to 20 em in diameter, decompound, rather lax. Spikelets 3 or more 
