PLANT IMPROVEMENT, GOOD SEED 29 



ter, Russian tumbleweed, the large sunflower, horseweed 

 or fleabane, ragweed, Spanish needles, buffalo bur, purs- 

 lane, cocklebur, corn cockle, mustard, chickweed, and field 

 dodder. 



The annual weeds are more commonly found in with 

 annual crops such as grain, com, potatoes, and garden 

 annuals; this is chiefly because the weed seeds sown each 

 year by the plants find ready lodgment in the freshly plowed 

 or cultivated fields and gardens. 



FIG. 14. Seeds mounted in holes in heavy pasteboard between two pieces of 

 glass held with paper binding. A tripod lens used for seed study. (Agricultural 

 Education.) 



One of the easiest ways to get rid of a bad field of annual 

 weeds is to rotate the crops by thickly seeding the field to 

 clover or grasses. Annual weeds are seldom found in such 

 fields, particularly after the first cutting of the hay. 



Biennial weeds are those plants which live two years, 

 the first year making a vigorous growth and storing some 

 nourishment, but bearing no .blossoms nor seeds until the 

 second summer. There are not many common kinds of 

 weeds in this group. Burdock, teasel, bull thistle, wild 

 carrot (Fig. 13a) and parsnip are common biennial weeds. 



Perennial weeds live several years and bear blossoms 



