38 



THE INDIANA WEED BOOK. 



In a number of weeds, as the common ragweed and field sorrel, 

 the stamens and pistils are borne in separate flowers. Those flow- 

 ers with stamens only are called staminate or sterile flowers, 

 whether the calyx or corolla be present or not, while those with 

 pistils only are pistillate or fertile flowers. In the ragweed these 

 two kinds of flowers are borne on the same plant and when so 

 borne the plant is said to be m.once-cious (of one household). In 

 the field sorrel they are on separate plants and in this and similar 

 cases the weed is called dioecious (of two households). If both sta- 

 mens and pistils are absent, as in the ray flowers of some Com- 

 positse weeds, the flowers are neutral. In the corn cockle the sta- 

 mens are 10 in number, separate, and bcrne en the stalk of the 



Fig. 12. Showing forms of pistils and ovaries: a, b and c, simple pistils; a, pistil of a single leaf, the ovary 

 cut across with the ov L les borne on the central suture; 6, pistil of marsh mai igold which has opened and shed its 

 seeds; c, 3 simple pistils of one flower; d-i, corn-pound pistils; d, of common St. Johnswprt, showing the three 

 separate styles and 3 cells of ovary; e, of shrubby St. Johnswort, showing the styles united, but the cells the 

 same; /, of spiderwort showing the 3 cells each with a s ; ngle ovule; g and h, of chickweed showing 3 styles, 1 cell 

 and ovules on a central colamn; t, a pistil showing the ovary, /, the style, g, and the stigma, n. (After Gray.) 



ovary, and the anthers open by lengthwise valves to discharge the 

 pollen. 



The pistils, or female parts of the flower, which produce the 

 young or unfertilized seeds called ovules, form the innermost set 

 of the essential organs. In number the pistils vary greatly ac- 

 cording to the species of plant. The flowers of some plants, as those 

 of the pea or clover, have a single simple pistil, while a buttercup 

 has many. Such simple pistils consist of a single modified leaf, the 

 carpel, folded together and containing one or many ovules. A 

 compound pistil, as that of the corn cockle, consists of two or more 

 carpels joined together. Each pistil is made up of two or three 

 parts. The two parts always present are the ovary or enlarged 

 part at base which contains the ovules, and the stigma which is 



