110 A FLORA OF MANILA 



4. Rachis glabrous. 



5. Leaves very short, less than 5 cm long; spikelets crowded. 



8. C. malaccensia 

 5. Leaves long, sometimes equaling the, stem; spikelets laxly 



disposed 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 globose 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. radiatua 



1. C. difformis L. 



A tufted glabrous annual 10 to 40 cm long, the stems sharply 3-angled at 

 the top. Leaves rather flaccid, somewhM 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 cm 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 ^umes about 0.6 mm 

 long, obtuse, brownish. Nutlets about 0.6 mm long. 



In open wet grass Ifinds, 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-flowered, 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, fl. all the year ; through- 

 out the Philippines. All warm countries; a characteristic rice-paddy weed. 



*3. C. FLABELLiPOKMis 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 sessilp 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 cm in diameter, decompound, rather lax. Spikelets 3 or more 



