456 COMPOSITAE (COMPOSITE FAMILY) 



appearance. Flowers of two kinds, the staminate heads in crowded 

 spike-like recemes at the summit of the plant and in its upper 

 axils ; the involucres top-shaped, formed of five to twelve united 

 bracts, and containing six to twenty small, greenish flowers. 

 Below, in the axils, concealed by clustering bracts, are the fertile 

 involucres, each one containing a single flower, the elongated 

 branches of its style protruding from 

 the closed and pointed crown ; when 

 mature these involucres form hard 

 achene-like fruits, about an eighth of 

 an inch long, ovoid, with a beaked 

 crown, surrounded by four to six spiny 

 points. Once in the soil, they sur- 

 vive for years, springing up when 

 opportunity offers ; they are a com- 

 mon impurity of grain and grass seed 

 and are also distributed in baled hay. 

 (Fig. 318.) 



Means of control 



The thin, softly hairy, and wide- 

 spread foliage of young Ragweed is 

 very susceptible to injury from chem- 

 ical sprays, and an application of 

 Copper sulfate or Iron sulfate will 



kill the plants in multitudes without 

 FIG. 318. Common Ragweed . . , 



(Ambrosia artemisiifolia). X i m J ur ^ tO the S raSS . r S ram am n S 



which they are growing. In clover 



fields the crop is slightly injured but recovers from the roots, 

 which the weed-seedlings seldom do. Infested clover fields 

 that are not treated should be cut early before the flower- 

 ing of the weed, as its pollen is extremely bitter and "cuts 

 the quality" of the hay even more than its dried young stalks. 

 Stubbles should have surface cultivation directly after harvest 

 so as to encourage germination of seeds in the soil, when the 

 young plants may be killed with the harrow, or they may be 

 plowed under for humus. In cultivated ground tillage should 



