22 Rydberg : Studies on the Rocky Mountain flora 



usually been known as Lactuca Scariola L., which name has in- 

 cluded all the prickly lettuces found introduced in North America, 

 viz., L. Scariola L., L. virosa L., L. saligna L., etc. The plants 

 with merely toothed leaves were referred to L. virosa L. by Dr. 

 N. L. Britton, but Mr. L. F. Dewey of the United States Depart- 

 ment of Agriculture contends that it is not L. virosa but L. Scariola 

 integrata Gren. & Godr. Mr. Dewey is followed by Robinson & 

 Fernald in Gray's New Manual. So also by Professor Nelson, 

 but he regards it as specifically distinct from L. Scariola and 

 proposes the name L. integrata (Gren. & Godr.) A. Nels. This 

 was altogether unnecessary for L. Scariola integrata Gren. & Godr.* 

 was based on L. augustana All.f Allion gives a good figure. 



Linnaeus in his first edition had only one species, Lactuca 

 virosa, with three varieties. In the second edition L. Scariola is 

 adopted for L. virosa var. 8 of the first edition. Both L. virosa 

 and L. Scariola are based on figures in Morison's Historia, and 

 the figure cited under L. virosa resembles indeed very much the 

 more common plant introduced in the Rocky Mountain region, 

 much more so than Allioni's plate of L. augustana does. The 

 difference between L. virosa and L. Scariola given by Linnaeus 

 is that the former has toothed horizontal leaves while in the latter 

 they are pinnatifid and vertical. The plant answering the descrip- 

 tion of L. Scariola has been collected in Utah and Montana but 

 the plant with merely toothed leaves is more common. Mr. 

 Dewey's contention may be correct as far as the plant around 

 Washington and Boston is concerned, but I think the plant of the 

 Rockies and the Pacific Slope is L. virosa. So far as I know, the 

 leaves are not turned on edge as they are in L. Scariola and 

 Professor Nelson describes the achenes of his L. integrata as being 

 dark-colored instead of pale. Dewey described the achenes of 

 Lactuca virosa as being darker and broader than in L. Scariola, 

 while he could not find any differences between those of the latter 

 and the var. integrata. There is another character which helps to 

 distinguish L. virosa and L. Scariola. In the latter, the branches 

 of the panicle are inclined to be racemiform, while in L. virosa 

 they are more branched with more or less diverging branchlets. 



*F1. Tran. 320. 1850. 

 fFl. Pedem. 1: 224. 1785. 



