RYDBERG: Rocky MOouNTAIN FLORA 551 
CARDUUS PLATTENSIS X UNDULATUS 
The specimen cited below was sent me by Mr. Osterhout, who 
suggested that it was a hybrid of Carduus plattensis Rydb. and 
C. undulatus Nutt. It has the head of the former, but somewhat 
smaller and with narrower and less viscid bracts. The leaves 
also are those of that species but approach those of C. undulatus. 
CoLorapo: Thompson’s River, Larimer Co., Aug. 16, 1905, 
Osterhout 3087. 
There are many features that suggest hybridity in Carduus 
perplexans Rydb. In the original description, attention was 
directed to its relationship to C. Centaureae (= C. americanus 
Greene) and also to the C. altissimus group. At that time I was 
inclined to regard it as a hybrid between C. americanus and C. 
jilipendulus, but the broad leaves seemed to contradict such a 
disposition. 
Since that time I have been inclined to regard it as a hybrid 
of C. laterifolius Osterhout and C. filipendulus, as the former 
has broad leaves resembling those of C. perplexans. The bracts, 
erose-tipped as they are, are not much like those of C. laterifolius. 
Mr. Osterhout suggests that it might be a hybrid of an undescribed 
species, specimens of which he has sent me. In these the bracts 
resemble those of C. perplexans very much and the flowers are 
also red; but the leaves are narrow and deeply pinnatifid. This 
species and C. filipendulus could scarcely produce a hybrid like 
C. perplexans. 
All the supposed hybrids given above were collected in Colo- 
rado. Besides these the following are in the herbarium of the 
New York Botanical Garden from neighboring states. 
CARDUUS MEGACEPHALUS X OCHROCENTRUS 
There seem to be two rather distinct forms included in Carduus 
ochrocentrus. As both are found in Texas and New Mexico and 
I have not seen the type specimen, I am uncertain which of the 
two is C. ochrocentrus proper. One of them extends northward to 
Nebraska and northern Colorado and is the only one found within 
the range of my studies. For the present I regard this as C. 
ochrocentrus, until further information can be had. It is charac- 
terized by strongly decurrent and strongly spinose, crisp leaves, 
