17 



fields, have been sent in for identification. The Russian Thistle is a very 

 serious pest in several of the Western States, and is found in the Prairie 

 Provinces, but has not yet been reported as being very troublesome 

 there. The plants, when ripe, break off at the surface of the ground and 

 are rolled long distances by the wind, scattering their numerous seeds on 

 their journey. It is this tumbling habit that makes this weed particularly 

 adapted to the prairie lands of the West, and it probably will never be 

 a serious pest in Ontario where fences, trees and other obstructions will 

 prevent its being spread far and wide by the wind. 



Description. The Russian Thistle is a native of Europe and West- 

 ern Asia. It is a nearly smooth, bushy branched annual, from i to 3 

 feet high. Mature plants are more or less spherical in form. The stems 

 and branches are red in color. The leaves are awl-shaped, one to two inches 

 long, soft and fleshy when young, very prickly pointed when mature. 

 The flowers are inconspicuous, being small, without petals, and solitary 

 in the axils of the leaves. The seeds are about 1-12 of an inch long, 

 obconical in general outline, with a cup-shaped depression at the upper 

 end in the centre of which is a pointed projection, color dull grey or 

 green, embryo spirally coiled. 



Fig . 16. Seeds of Russian Thistle. 



(a) Complete seeds. 



(b) Embryo. 

 Enlarged about 12 v os. 



Fig. 17 . Seed of Field Pepper Grass or Cow 

 Cress . 

 Enlarged about 12 times. 



Eradication. The Russian Thistle being an annual weed is not hard 

 to exterminate. If once cut off at the surface of the ground it never grows 

 again, and hence in well cultivated fields it is not likely to prove a pest. 

 The chief danger lies in neglect. A single plant produces an enormous 

 number of seeds, and if a few specimens are allowed to mature they will 

 seed down a whole field and cause serious trouble the following year, 



2 Bull. 168. 



