HITCHCOCK AND CHASE TEOPICAL NORTH AMERICAN PANICUM. 473 



DICHOTOMIFLORA . 



Three species of this group, Panicum aquaticum, P. sucosum, and P. elephantipes, 

 are found to be perennial. 

 Plants annual. 



Panicles narrow, less than 1 cm. wide 14. P. vaseyanum. 



Panicles open, the branches ascending or spreading. 



Sheaths glabrous 15. P. dichotomiflorum. 



Sheaths papillose-hispid 16. P. bartowense. 



Plants perennial. 



Fruit not acuminate; panicles rarely over 18 cm. long. . . 17. P. aquaticum. 

 Fruit acuminate; panicles as much as 40 cm. long, rarely 

 less than 20 cm.; culms succulent. 

 Spikelets about 3.5 mm. long; fruit abruptly acumi- 

 nate 18. P. sucosum. 



Spikelets 4 to 5 mm. long; frmt long-acuminate; 



culms very succulent 19. P. elephantipes. 



14. Panicum vaseyanum Scribn. 



Panicum vaseyanum Scribn.; Beal, Grasses N. Amer. 2: 140. 1896; Contr. U. S. 

 Nat. Herb. 15:47. 1910. 



DISTRIBUTION. 



Moist open ground, around ponds and de- 

 pressions in prairies, northern Mexico. The 

 type specimen from Chihuahua. 



Chihuahua: Base of Sierra Madre, 

 Pringle 1415. Minaca, Hitchcock 

 7757. 



Aguascalientes: Aguascalientes, Hitch- 

 cock 7491, Am£r. Gr. Nat. Herb. 15. 



Jalisco: Guadalajara, Hitchcock 7315. 



\ "<So ';' ( ', i 



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-Ctf^ 



V \V/^^7v 







r_ c^^aSz 



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Fig. 25.— Distribution of P. vaseyanum. 



15. Panicum dichotomiflorum Michx. 



Panicum dichotomijlorum Michx. Fl. Bor. Amer. 1:48. 1803; Contr. U. S. Nat. Herb. 

 15:48.1910. 



The South American Panicum chloroticum Nees, included in the Revision in P. 

 dichotomiflorum, is a distinct species, or possibly a subspecies. It is not known from 

 north of Brazil. 



distribution. 



Moist ground along streams and a 

 weed in waste places and in cultivated 

 soil, Maine to Florida and California 

 (rare in the West), and in the West 

 Indies and Panama. The type speci- 

 men from the AUeghenies. 



Panama : Near Chepo, Pittier 4614. 



Gatun, Hitchcock 7977. 

 Bermuda: Hamilton, Millspaugh 

 126. 

 Bahamas: Hog Island, Eggers 4405, 4512. Watlings, Geogr. Soc. Baltimore 489. 

 Nassau, Curtiss 177. Cat Cay, Brace 3742. 



Fig. 26.— Distribution of P. dichotomiflorum. 



