38 
IOWA ACADEMY OP SCIENCE 
abundalit in Northern Iowa than in the southern part of the state. For 
many years the plant rarely produced seed in this state, though the 
seed was not infrequently produced on plants found along the shores of 
Lake Michigan in Wisconsin. It now seems to have developed the seed 
habit in Iowa, though by no means as frequent as in Canada and in 
Europe. The Woolly Thistle {Cirshim canescens) indigenous to the 
country and to the south to western Iowa to the Kocky Mountains in 
Colorado and Montana, is common east of Calgary. The Field Thistle, 
(Cirsium discolor) though a common weed in Iowa and Minnesota, is 
less common in the Red River Valley and only reaches across the bor- 
der into Manitoba. The Bull Thistle (Cirsiiim lanceolatiim) is not 
common at any point east of Calgary to Winnipeg but on the west 
slope of the Rockies in the valleys of the Selkirks and Cascades to Van- 
couver, Victoria, (B. C.) Seattle, Everett and Seattle it is a common 
weed. It is common also in the Great Basin Country of Utah and in 
Montana and Idaho. The AVhite Weeds, {Erigeron ramosus and E. 
strigosus) so common everywhere in the Mississippi Valley from ]\Iis- 
souri north to Minnesota and west to Nebraska, are not to be counted 
among the conspicuous weeds of that country. The Horseweed, which 
is sometimes called the Marestail, is not abundant in the great wheat 
belt of Canada, although in British Columbia it is abundant in clear- 
ings and cultivated fields. The White Weeds give an interesting aspect 
to the meadows in Iowa in June. 
The common weedy Sunflower H. petiolaris and the H. annuus are 
less frequently found on the Pacific Coast, but common in Kansas and 
Nebraska westward to the Rockies. On the prairies about Winnipeg 
west to Moose Jaw and Medicine Hat the E. maximilianii is abundant. 
This species also occurs in Northwestern Iowa through Minnesota to 
Manitoba. The Blue Lettuce (Lactuca ptUchella) is abundant about 
Winnipeg and southward but not abundant in Saskatchewan and Al- 
berta, common from western Iowa and westward. Prickly Lettuce 
{Lactiica Scariola) is common from Kamloops to Victoria and Seattle, 
and on the Pacific Coast in California and eastward. In some places 
more common than the variety integra which is the common form in the 
Mississippi Valley. The species is rare in Ipwa, although the variety 
is abundant. The rapid spread of the variety in Northern United 
States since 1877 shows how remarkably well it has adapted itself to 
the more humid and drier regions of the country. The Pine-apple Weed 
{Matricaria suaveolens) is common from Sicamous Junction, Revel- 
stoke, B. C., to Victoria, Vancouver, B. C., and Seattle. This weed is 
common on the Pacific slope, throughout the interior of the continent in 
