GENERA OF GRASSES OF THE UNITED STATES. 



231 



Panicum virgatum L. (fig. 139) switch-grass, an erect perennial 3 to 

 5 feet tall, with open spreading panicle, is common in the eastern half 



Fio. 139. Switch-grass, Panicum virgaiwm. Plant, X I ; two views of spikelet and 



fertile floret, X 10. 



of the United States. It is a constituent of prairie hay. Panicum 

 bulbosum H. B. K., of the Southwest develops well-marked corms 



