HITCHCOCK AND CHASE-—TROPICAL 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. 
Her MRSA DROUSELotee ae Hamiisc aie sleet -lein(cjn wicacic,o atuys 15. P. dichotomiflorum. 
NHerths papillose-MISpIG. seo. asec. Se oe oe ne. 6, WP. 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- 
AUC ees Meena see Re A aie ts oe slau ake 18. P. sucosum. 
Spikelets 4 to 5 mm. long; fruit long-acuminate; 
CULMEWETVESUCCHICN bso) se cee Ne cies sec ea 6 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. 
CuinuAHUA: Base of Sierra Madre, 
Pringle 1415. Mifiaca, Hitchcock 
7757. 
AGUASCALIENTES: Aguascalientes, Hitch- 
cock 7491, Amer. Gr. Nat. Herb. 15. 
Jauisco: Guadalajara, Hitchcock 7315. Fig. 25.—Distribution of P. vaseyanum. 
15. Panicum dichotomiflorum Michx. 
Panicum dichotomiflorum Michx. F1. 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 
Indiesand Panama. The type speci- - 
men from the Alleghenies. 
Panama: Near Chepo, Pitter 4614. 
Gatun, Hitchcock 7977. 
Breruupa: Hamilton, Millspaugh 
126. 
Banamas: Hog Island, Eggers 4405, 4512. Watlings, Geogr. Soc. Baltimore 489. 
Nassau, Curtiss177. Cat Cay, Brace 3742. 
Fig, 26,—Distribution of P. dichotomiflorum. 
