94 BULLETIN 772, U. S. DEPARTMENT OF AGRICULTURE. 



divides into two parts, which stand side by side below the spikelet, 

 the second glume being suppressed. 



In the group of Elymm virginicus L. and its allies the glumes are 

 indurate at the base and bowed out. They stand in front of the 

 spikelet rather than at each side, so that the contiguous glumes of 

 the pair of spikelets are not back to back but side by side. In 

 E. arenarius L., E. glaucus Buckl., and allied species, the glumes are 

 less distinctly in front of the spikelets. The rachis of the spike is 

 usually continuous but in E. saundersii Vasey, and, to a less extent, in 

 E. macounii Vasey, the rachis disarticulates, showing a transition 

 to Sitanion. In many species, such as E. simplex Scribn. and Merr., 

 and E. salina Jones (named from Salina Pass), the middle spikelets 

 are in pairs, but those toward the base and apex of the spike are 

 single at the nodes. Such species are a transition to Agropyron. 

 On the other hand Agropyron smithii often has one or more pairs 

 of spikelets and may be considered a transition to Elymus. But in 

 the former species the glumes are narrow or almost subulate, which 

 shape is to be found in Elymus rather than in Agropyron. The 

 spikelets are usually not more than two at each node of the rachis, 

 but in E. trlticoides Buckl. there are often, and in E. condensatus 

 Presl. usually, more than two spikelets at each node. Sometimes in 

 the latter species (rarely in the former) the spike is branched so 

 that the inflorescence is a condensed panicle instead of a spike. 

 Elymus caput-medusae L. is an annual introduced from Europe ; the 

 other species are native perennials. Some species form extensively 

 creeping rhizomes, such as Elymus mollis Trin., of the sandy sea- 

 coasts of northern North America, E. flavescens Scribn. and Smith, 

 of the interior dunes of the Columbia River basin, and E. triticoides 

 Buckl., of alkaline soil of the Western States. Elymus canad^msis L. 

 (fig. 47) and E. virginicus, usually called wild rye, are common in 

 the eastern half of the United States. The first has a bushy nodding 

 head ; the latter an erect, stiff head. 



The species of Elymus are for the most part good forage grasses, 

 and in some localities form a part of the native hay. In the wooded 

 areas of the Northwest, E. glcaivus Buckl. is one of the valuable sec- 

 ondary species on the ranges. It has flat, thin leaves, erect awned 

 spikes, broad glumes, and no rhizomes. 



38. SITANION Raf. 



Spikelets 2 to few flowered, the uppermost floret reduced, sessile, 

 usually 2 at each node of a disarticulating rachis, the rachis break- 

 ing at the base of each joint, remaining attached as a pointed stipe 

 to the spikelets above; glumes narrow or setaceous, 1 to 3 nerved, 

 the nerves prominent, extending into one to several awns, these 

 (when more than one) irregular in size, sometimes mere lateral 



