8 THE MONTANA EXPERIMENT STATION. 



A third class requires the agency of animals to assist their 

 migration. Some of these have hooked, barbed or awned fruit 

 which cling to the fur and wool of stock and hence are particularly 

 injurious to the wool industry of the state. Among them may be 

 mentioned the cuckleburs, beggar-ticks, wild liquorice, buffalo-bur, 

 spear-grass and foxtail. The weeds so common along streets and 

 highways, in yards and pastures, are distributed mainly by the 

 mud of passage, which adheres to the feet of animals and the 

 wheels of vehicles, while the adhesiveness of a considerable num- 

 ber is further increased by developing a gummy secretion from 

 their outer coat or envelope to assist in the process. These seeds 

 are usually small and frequently depend in part upon water for 

 their extension. Those with mucilaginous envelopes are the 

 plantains, shepherd's purse, bird-seed (Lepidium), Matricaria, 

 Monolepis and Euphorbia, while the sticky contents of the berry 

 of the wild tomato serve a similar purpose. Many of these weeds 

 are edible and have small seeds with impervious coverings, which 

 enable them to withstand the various processes of digestion and 

 they are thus scattered in the offal of animals. Hence barn-yard 

 manure is a prolific source of weeds and always tends to restock 

 our fields with these pests. 



But the agencies above enumerated tend only to scatter weeds 

 already established in a communit}', while foreign species come in 

 chiefly through the agency of man, and it is against these intro- 

 ductions that we are able to guard most effectively. A large 

 number of these imported weeds first reach us through the rail- 

 ways traversing the state, being transported in merchandise, in 

 hay and in the bedding of stock cars and these seeds are dropped 

 en route or in the transfer of goods at the several 

 stations. Hence, it is a matter of common observation that new 

 weeds are frequently first observed along the railways and in the 

 vicinity of such stations. The Russian, the Canada and the 

 Scotch bull thistles seem to arise mainly from this source. 



It is probable that the chief means of foreign infection is 

 through the importation of impure seed. New weeds are con- 

 stantly appearing in our fields and gardens traceable directly 

 to this source and all such weeds should be promptly exterminated 

 before they secure a foothold. 



