352 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
Plants perennial. 
Plants cespitose...........2...20222.0.02.02...... 2. C. multifidum. 
Plants stoloniferous. 
Spikes dimorphous; sterile lemma cleft less 
than half way.........2..25-0.0.0.0.... 3. C. erectum. 
Spikes not dimorphous; sterile lemma cleft 
nearly to the base ........0....2...... 4, C. stoloniferum. 
Spikes consisting of more than 3 spikelets. (But  in- 
cluding B, uniflora, which has but 1 spikelet.) 
(BouTELoua, p. 363.) 
Spikelets pectinately arranged at maturity (Subgenus 
CHONDROSIUM). 
Spikes normally less than 4. 
Spike 1. 
Plants annual. 
Spikes comparatively narrow. (North 
American).................... 1. B. procumbens. 
Spikes comparatively wide. (South 
American).................... 2. B. simplex, 
Plants perennial. 
Stoloniferous.......22-.............. 3. B. stolonifera. 
Cespitose.....2..... 1. B. scorpioides. 
Spikes normally 2, often | or 3, or even 4, 
seldom more than 4. 
Glumes tuberculate; rachis prolonged 
beyond the spikelets as a naked 
point.@ 
Internodes hirsute-villous............ 5. B. hirticulinis. 
Internodes not hirsute-villous....... 6. B. hirsuta, 
Glumes not tuberculate; rachis not. pro- 
longed. 
Culms annual......2.2....0.0202.... 7. B. gracilis, 
Culms in part perennial, 
Culms erect-branching........... 8S. Bb. breviseta. 
Culms geniculate-branching..... 9. B. ramosa. 
Spikes normally 4 or more. 
Glumes hairy-villous.........222.2......... 10. B. parryi. 
Glumes not hairy-villous. 
Plants annual, 
Awns of fertile lemma comparatively 
short.....222.202.00.2........ U1. B. barbata, 
Awns of fertile lemma comparatively 
long... 12. B. arenosa, 
Plants perennial, 
Low, 10 to 30 em. high. 
Rudiment naked........... 2... 13. B. trinii. 
Rudiment hairy-tufted......._. 14. B. sonorac. 
Larger plants 30 to 50 em. high. 
Culms villous; stoloniferous..... 15, B. eriopoda, 
Culms not villous; cespitose, 
Base delicate............... 16. B. rothrockit. 
Base strong, harsh, scaly, 
rhizomatous.......... ly. B. karwinski. 
@ Forms of B. gracilis have tuberculate glumes, but never a prolonged rachis. 
