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 
Fic. 318.— Common Ragweed 
(Ambrosia artemistifolia). 
fields the crop is slightly 
xt 
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 
injury to the grass or grain among 
which they are growing. In clover 
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 
