10 Rhodora [JANUARY 
the Gray Herbarium of Harvard University. These were identified 
as Lactuca scariola L., and a description of the plant under this name 
appeared in the 5th edition of Gray’s Manual, published in 1868. 
From 1880 to 1885 the plant was reported from several localities in 
Ohio, Indiana, Illinois and southern Michigan. It seems probable 
that there were several independent introductions of the seed mixed 
with poorly-cleaned field seeds. It became abundant in the regions 
where clover seed and grass seed are largely produced, and then its 
distribution rapidly increased. Within 30 years from the date of its 
first recorded appearance in this country it had reached every state 
and territory in the land, and in many localities it quickly came to be 
recognized as the most prolific and aggressive weed that the farmers 
had ever been troubled with. From 1893 to 1897 most alarming 
reports in regard to it were received at the Department of Agriculture. 
In some instances it was stated that valuable farms would have to be 
abandoned unless some means could be devised for keeping it in 
check. The danger period seems now to be past. The prickly let- 
tuce has either found natural enemies which keep it in check, or for 
some reason it has lost much of its aggressive character. It is 
becoming much less abundant in regions where it formerly occupied 
nearly all the waste land and many of the cultivated fields, and the 
individual plants are generally less robust and less prolific than they 
were six to ten years ago. 
All of the scores of specimens of the weed examined agreed with 
each other in their essential characters, and all were called Z. scariola 
until within the past three years. In August, 1901, a specimen was 
received at the Department of Agriculture for identification, from 
Plainville, Hamilton Co., Ohio. This specimen differed from all 
others that had been examined in having runcinate or pinnately-lobed 
leaves. A careful study of the early descriptions proved that this 
form must be the true Z. scariola, of Linnaeus. If this was Z. 
scariola, the common form with unlobed leaves certainly was not, and 
for the first time in its history of nearly 40 years as a weed in this 
country its real identity became a matter of importance. A reference 
to the descriptions of Lactuca given by Linnaeus, and to some of 
the plates referred to, seemed to indicate that it was Lactuca virosa 
L. This is one of the species included with Z. scariola by most 
English authors, who regard it as an entire-leaved form of that spe- 
cies. Dr. Britton’s Manual of the Flora of the northern States and 
