WEEDS AND POISONOUS PLANTS 



333 



But besides these methods of seed and fruit distribution 

 which are common to many plants, there are a number of 

 others that are peculiar to weeds and must be specially- 

 guarded against. For instance, weed fruits and seeds are 

 often carried into new regions by railway trains; and one 

 often finds newly introduced weeds and other plants growing 



Fig. i88. — .\ mixture of seeds commonly found in low-grade alsike 

 clover seed: a, alsike clover; h, white clover; c, red clover; i, yellow 

 trefoil; e, Canada thistle ; /, dock ; g, sorrel ; A, buckthorn ; i, rat-tail plan- 

 tain; ^, lamb's quarters; /, shepherd's purse ; m, mayweed; re, scentless 

 camomile ; o, white campion ; p, night-flowering catch-fly; q, ox-eye daisy; 

 r, small-fruited false flax; s, cinquefoil ; i, two kinds of peppergrass; 

 M, catnip; o, timothy; x, chickweed ; y, Canada bluegrass; z, clover 

 dodder; i, mouse-ear chickweed; 2, knot-grass; j, tumbling amaranth; 

 4, rough amaranth ; 5, heal-all; 6, lady's thumb. After Hillman. 



beside railway tracks, and perhaps spreading gradually from 

 there into neighboring fields. When weeds grow undis- 

 turbed among cultivated plants, their seeds are likely to be 

 harvested with the crop ; as a result, the weed seeds are 

 distributed with those of the harvested crop, as chess seed 

 with wheat, wild oats with cultivated oats, and dodder with 

 clover or alfalfa seed; or the seeds, like those of many 



