8 THE RUSSIAN THISTLE. 



is seriously interfered with. The annoyance and positive injury to men 

 and animals which they cause by their rigid spines is undoubtedly 

 greater than that caused by any of the true thistles. A trouble of 

 another kind results from their being blown during prairie fires across 

 fire breaks that would otherwise be ample protection to stacks or 

 buildings. 



"Warning to Pacific Coast Wheat-growers. ^&$\, of the Rocky 

 Mountains the thistle is already so widely distributed that its continued 

 progress in that region is inevitable. Its advent in Idaho and California, 

 however, is a far more serious matter. The Rocky Mountains present a 

 great natural barrier which the thistle will not easily pass, except by 

 artificial conveyance. With the natural conditions thus favorable to its 

 exclusion, and with a full knowledge of the disastrous nature of the 

 scourge, it is almost criminal to allow it to become established west of 

 the Rockies. To the Pacific Coast the Sierra Nevada and Cascade 

 mountains afford additional protection, but some seed will be sure to 

 find its way over this barrier also, especially if the thistle is allowed to 

 obtain a hold in the Great Basin. In view of these facts, the California 

 wheat-grower should take precautions against the weed, opposing both 

 its direct introduction into California from the plains east of the Rockies 

 and its gradual advance by way of the Great Basin. 



"The plant is an annual, easily killed at any time during the growing 

 season. It produces no seed before the middle of August or first of 

 September, and the seed is short-lived. The circumstances, therefore, 

 are exceptionally favorable for its being checked, or even exterminated. 

 In order to secure a complete extirpation these two conditions must be 

 fulfilled: 



"1. No Russian thistle shall be allowed to produce seed. 



"2. There must be concerted action throughout all the infested area. 



"If the Russian thistle, wherever found, should be killed before it 

 produces seed during three successive years, the pest would in all 

 probability be completely exterminated; for the experiments already 

 made indicate that the vitality of the seed is lost within that period. 

 But since the ground is so easily reseeded from a neighboring crop, if 

 action is not taken everywhere and at one time the work will have to 

 be done over indefinitely. 



"In the absence of universal concerted action, as extensive coopera- 

 tion as possible should be secured ; and at all events each farmer should 

 protect his own farm as well as he may, in doing which he will also 

 avoid injuring his neighbor. The want of cooperation is a great dis- 

 advantage. Farmers in some instances have so far succeeded in keeping 



