TORREYA 



September, 1917. 

 Vol. 17 ^°- 9 



THE INTRODUCTION OF FOREIGN WEEDS IN BAL- 

 LAST AS ILLUSTRATED BY BALLAST-PLANTS 

 AT LINNTON, OREGON 



By J. C. Nelson 



One of the striking features of the flora of that part of Oregon 

 lying west of the Cascade Alountains is the very large proportion 

 of introduced plants which have become fully established. 

 Many foreign plants which are common in the Eastern States, 

 but which disappear wholly or largely in the Central States and 

 the Great Plains, reappear on the Pacific coast. The high 

 humidity and mild winters of this region afford exceptionally 

 favorable conditions for the propagation of these immigrants, 

 and make it difficult to eradicate them when once established. 

 The similarity of climatic conditions to those of Western Europe 

 has enabled a very large number of plants indigenous to that 

 region to obtain a foothold in western Oregon. Mr. John 

 Burroughs has called attention to the surprising tenacity of 

 the plants and animals of the British Isles when forced to struggle 

 for existence with our native species. Unfortunately the plants 

 which tend to survive in this contest are most often those which 

 are not only of no value, but are a positive menace to the farmer 

 and stockman. The vilest and most obnoxious weeds seem 

 specially favored in the struggle, and spread with such surprising 

 facility that under the prevailing methods of cultivation it is 

 impossible to make head against them. 



The precise agency by which these foreign plants are first 

 introduced cannot usually be determined with any certamty. 

 They are often encountered for the first time in regions remote 

 [No. 8, Vol. 17 of Torreya'. comprising pp. 131-150, was issued 14 August, 191 7-] 



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