WEED MIGRATION 



699 



Fig. 538A. Caltrop (Tribulus terristris). 



(Photographed by Colburn.) 



Scherer and others record the occurrence of Solanum rostratum 

 in Germany (1883) and in France. 



In Pflanzenleben, Kabsch says, "There are many illustrations of 

 plant iromigrations and spreading of plants in Europe, but so far 

 as I know they have never occupied the soil to the same degree in 

 Europe as in America. Most of our weeds of fields, like the cereals 

 among which they grow, are of foreign origin, as star thistle 

 {Centaurea cyanus), corn cockle {Agrostemma githago), charlock 

 {Baphanus raphcmistrum) , Myagrum, etc." There are many other 

 weeds of grain fields that are of similar origin that are not men- 

 tioned by Kabsch. Among them are the common mustard {Brassica 

 arvensis), common vetch {Vicia sativa), darnel {Lolium temulen- 

 tum), Eussian thistle {Salsola kali var. \enuifolia), pennycress 



