302 AMERICAN MIDLAND NATURALIST 
or Flora of Montana), and its barbellate outer bristles place 
our plant with Cirsium nebraskense. 
- It would certainly have been in better harmony with the 
conception of these plants viewed through North Dakota glasses 
if the variety had been discovered first and become the species. 
3. CIRSIUM MEGACEPHALUM. 
Cnicus undulatus megacephalus Gray, Proc. Am. Acad. 10: 
42 (1874). 
Carduus megacephalus A. Nels., New Manual of the Botany 
of the Central Rocky Mountains, p. 587 (1909). 
Cirsium megacephalum Lunell. 
This is a short, stout and rigid plant, probably not widely 
distributed within the state. The only locality from which it 
is known to me is Pleasant Lake, Benson County, where it is 
growing sparsely along the railroad. 
4. CIRSIUM MUTICUM. 
Cirsium muticum Michx., Fl. Bor. Am. II.: 89 (1803). 
This beautiful thistle grows in the sloughs of the Turtle Moun- 
tains, and has also been reported from Walhalla, Pembina County. 
5. Cirsium arvense var. HORRIDUM. 
Serratula arvensis L., Sp. Plant. ed. 1, p. 820 (1753). 
Cirsium arvense Scopoli, Fl. Carn. ed. 2. II, p. 126 (1772). 
Cirsium arvense var. horridum Wimmer et Grabowski, FI. 
Silesiaca II., p. 92 (1828). 
Known as Canadian thistle in this country, it got its variety 
name on account of its abundance of prickles, which in combina- 
tion with its nearly irrepressible tendency for spreading and its 
ability of suffocating almost any other vegetation make it one 
of the most formibable and pernicious weeds known. It grows 
not only in fields and pastures, but establishes itself in wet meadows 
and sloughs. I have one specimen from Colorado collected by 
Mr. Geo. E. Osterhout, and I do not know if the species grows 
on this continent. In Europe the variety is exceptional, and the 
species common almost everywhere. The latter is a comparatively 
harmless plant with short, sparse prickles or often nearly unarmed, 
and without apparent disposition for exclusive appropriation of 
large patches of ground, and many farmers do not know its name 
or ever noticed it, and Linnaeus referred it to the genus Serratula 
which is not even a thistle 
Leeds, North Dakota. 
