352 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Plants perennial. 



Plants cespitose 2. C. mullijidum. 



Plants stoloniferous. 



Spikes dimorphous; sterile lemma cleft less 



than half way 3. C. erectum. 



Spikes not dimorphous; sterile lemma cleft 



nearly to the base 4. C. stoloniferwn. 



Spikes consisting of more than 3 spikelets. (But in- 

 cluding B. unifiora, which has but 1 spikelet.) 

 (Boutelotja, 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 3. B. stolonifera. 



Cespitose 4. B. scorpioides. 



Spikes normally 2, often 1 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. hirticulmis. 



Internodes not hirsute-villous 6. B. hirsuta. 



Glumes not tuberculate; rachis not pro- 

 longed. 



Culms annual 7. B. gracilis. 



Culms in part perennial. 



Culms erect-branching 8. B. breiiseta. 



Culms geniculate-branching 9. B.ramosn. 



Spikes normally 4 or more. 



Glumes hairy- villous 10. B. parryi. 



Glumes not hairy- villous. 

 Plants annual. 



Awns of fertile lemma comparatively 



short 11. B. barbata. 



Awns of fertile lemma comparatively 



long 12. B. arenosa. 



Plants perennial. 



Low, 10 to 30 cm. high. 



Rudiment naked 13. B. trinii. 



Rudiment hairy-tufted 14. B. sonorac. 



Larger plants 30 to 50 cm. high. 



Culms villous; stoloniferous 15. B.eriopoda. 



Culms not villous; cespitose. 



Base delicate 1G. B. wlhrocl-ii. 



Base strong, harsh, scaly. 



rhizomatous 17. B. karwinskii. 



a Forms of B. gracilis have tuberculate glumes, but never a prolonged rachis. 



