HITCHCOCK AND CHASE—NORTH AMERICAN PANICUM. 89 
villous at the throat; ligules dense, 2 to 4 mm. long; blades ascending, 10 to 60 cm. 
long, 3 to 15 mm. wide, slightly narrowed toward the base, and gradually long-acu- 
minate, flat, sometimes pilose on the upper 
surface toward the base, rarely to the apex, 
margins scabrous; panicles long-exserted, 15 to 
50 cm. long, mostly one-third to half as wide, 
but sometimes contracted, or very loose and 
nearly as wide as long, usually many-flowered, 
the slender, scabrous, usually fascicled branches 
ascending or spreading, naked at base, repeat- 
edly branching along the upper half or two- 
thirds; spikelets rather short-pediceled, 3.5 to 
5 mm.,, rarely but 3 or as much as 6 mm. long, 
1.2 to 1.5 mm. wide, elliptic-ovate, acuminate, 
strongly nerved; first glume clasping, two-thirds 
to three-fourths the length of the spikelet, rarely 
equaling the sterile lemma, acuminate to cus- 
pidate, 5-nerved; second glume longer than the 
sterile lemma, both much exceeding the fruit, 5 to 7-nerved; fruit narrowly ovate, the 
margins of the lemma inrolled only at base. 
This species is well marked but variable. The blades are usually glabrousor 
pilose above near the base only. Sometimes, however, the entire upper surface or 
even both surfaces are pilose. Examples of this are: Minnesota: Mearns 743; 
Soutn Dakota: Thornber; Nepraska: Rydberg 1561; Kansas: Smyth92; Groraia: 
Tracy 3604, Harper 631; FLorma: Combs 597; ALABAMA: Carver 72; MISSISSIPPI: 
Chase 4459. 
The form named by Vasey P. virgatum confertum, with more or less compact panicles, 
is represented by: New Jersey: Scribner in 1895, Vasey in 1884, Ward in 1884; Vir- 
cinta: Knowlton in 1897; Norra Carona: McCarthy in 1885; FLoripa: Kearney 158. 
The size of the panicle is variable, in northern specimens being often much dwarfed. 
The branches may be stiffly ascending or laxly spreading or drooping, these characters 
not being coérdinate with others. The glaucous character also appears to be without 
Sienificance in separating forms, glaucous and green individuals growing under the 
same conditions. All these variations are connected by all shades of intergradation 
with the typical form. 
Throughout the western portion of the range of the species there is found, chiefly 
on sandy soil, a form with mostly single or loosely cespitose culms, often decumbent 
at base, pale green or glaucous foliage, and small panicles with ascending branches. 
We have been unable to separate this form as a subspecies because of the numerous 
intergrading specimens. The following, which are not cited under the distribution 
of the species, are representative of this form: SourH Daxora: Huron, Williams in 
1892; Bellefourche, Griffiths 395; White River, Wallace 3, 4, 5; Iowa: Cherokee 
County, Crozier in 1888; Nrepraska: Sidney, Plank 13; Mullen, Rydberg 1597; Kan- 
sas: Morton County, Hitchcock Pl. Kans. 570a; Texas: Tascora, Reverchon 2844; 
Channing, Williams 3061; CoLtorapo: Raton Mountains, Griffiths 5463; Arizona: 
Flagstaff, MacDougal 265; without locality, Lemmon 3154. 
The spikelets are frequently affected by a smut, this sometimes resulting in abnor- 
mal forms with spikelets in glomerules or with two to several staminate or abortive 
florets to a spikelet, as in Sandberg from Minnesota in 1891 and Brandegee from 
Colorado in 1878, 
Fra. 79.—P. virgatum. From type specimen 
in Gronovius Herbarium. 
DISTRIBUTION. 
Prairies, moist open ground, open woods and salt marshes, Maine to Wyoming and 
south to Florida and Arizona, southwest through Mexico to Costa Rica; also in the 
sermudas and Trinidad. 
Marne: Scarboro, Chamberlain 552. 
New Hampsuire: Walpole, Fernald 271 (N. E. Bot. Club Herb.). 
