14 BULLETIN 622, U. S. DEPARTMENT OF AGRICULTURE. 



and the other naked. Later, the trifurcate character was trans- 

 ferred to many forms, until H. v. trifurcatum is noteAvorthy only as 

 the parent form of trifurcate barleys. This illustrates the vital dif- 

 ference between the treatment of a group with only a few representa- 

 tives and one with many. The greater the number of forms, the 

 fewer are the characters that separate them. 



KEY TO THE VARIETIES. 



Following is the key to the varieties occurring under the four spe- 

 cies of barley : 



Hordeum vulgare. Barleys, with three fertile spikelets at each node, the lemmas 

 of both central and lateral florets bearing awns or hoods. 

 Kernels hulled. 



Lemmas awned. 



Kernels white, blue, or purple 1. pallidum. 



Kernels black 2. nigrum. 



Lemmas hooded. 



Kernels white, blue, or purple 3. horsfordianum. 



Kernels black 4. atrum. 



Kernels naked. 



Lemmas awned. 



Kernels white, blue, or purple 5. coeleste. 



Kernels black 0. duplmigrum. 



Lemmas hooded. 



Kernels white, blue, or purple 7. trifurcatum. 



Kernels black 8. aethiops. 



Hordeum intermedium. Barleys in which the lateral 

 florets are fertile but awnless. 

 Kernels hulled. 



Lemma of central floret awned or awnless. 



Kernels white, blue, or purple 9. haxtoni. 



Kernels black 10. mortoni. 



Lemma of central floret hooded. 



Kernels white, blue, or purple . 11. subcornutum. 



Kernels black 12. atricornutum. 



Kernels naked. 



Lemma of central floret awned or awnless. 



Kernels white, blue, or purple 13. nudiJiaxtoni. 



Kernels black 14. nudimortoni. 



Lemma of central floret hooded. 



Kernels white, blue, or purple 15. cormitum. 



Kernels black 16. subaethiops. 



Hordeum distichon. Barleys in which the lateral florets 

 are present but sterile. 

 Kernels hulled. 



Lemmas awned or awnless. 



Kernels white, blue, or purple 17. palmella. 



Kernels black 18. nigricans. 



Lemmas hooded. 



Kernels white, blue, or purple 19. august ispicatum . 



Kernels black 20. rimpauL 



