92 RypBERG: 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.t 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. 6 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. 
*F]. Tran. 320. 1850. 
TF, Pedem. 3: 224. 1735. 
