Rydberg: Studies on the Rocky Mountain flora 107 



•S. elymoides Raf., I think that the latter name should supplant 

 the other two. S. lanceolatum J. G. Smith from Montana and 

 S. marginatum Scribn. & Merrill from Wyoming are the two 

 species of the range best differentiated and seem to connect the 

 genus with Elymus. S. insulare was described from north- 

 eastern Utah, and 6 1 . ciliatum has been collected in Wyoming. 



ARACEAE 



This family is omitted altogether in the New Manual, although 

 Acorns Calamus is recorded in my Flora of Colorado and Lysichiton 

 camtschatcense (L.) Schott in my Flora of Montana. The former 

 has also been collected in Montana by Butler. 



LEMNACEAE 



Lemna perpusilla Torr. is included by Nelson in his Manual 

 with the remarks: "Frequent; 'northern Wyoming to New York." 

 So far as I know this is wholly an eastern species. Specimens so. 

 labeled from the Rockies, which have come under my observation, 

 are L. minor, L. minima, or L. cyclostasa, which all have been 

 confused with it. 



COMMELINACEAE 



Professor Nelson admits two species of Tradescantia and gives 



the following key: 



Freely branched ; filaments folded ; ovary pubescent in riblike lines, i . T. laramiensis. 

 Simple; filaments straight; ovary pubescent at the apex. 2. T. occidentalis. 



If these characters hold, as to separating the two species 

 known to Professor Nelson, the second one is not T. occidentalis, for 

 the specimen designated by Dr. Britton as the type of Trades- 

 cantia virginica occidentalis, viz., Rydberg 1380, from Thedford, 

 Nebraska, has a branched stem and an ovary pubescent not only 

 at the apex but almost to the base. It is not exactly like the 

 type of T. laramieyisis , however, for the lateral branches are 

 shorter than the stem proper, the sepals are broader, the leaves 

 broader, and the plant more glandular. In T. laramiensis the 

 lateral branches about equal the stem, giving the plant a flat top. 

 If these are specific characters, I do not know. If the two species 

 of the New Manual are distinct, the second one should bear the 

 name T. universitatis Cockerell, for it was this form that Professor 

 Cockerell described. 



