STUDIES OF SEED-PLANTS 



205 



B C 



FIG. 64. Compound pistils. 

 A, two pistil-leaves or car- 

 pels slightly united; B, 

 three united as to ovaries, 

 but with separate styles ; 

 C, three united into one 

 compound ovary and 

 style. (From Gray.) 



199. Simple and Compound Pistils. In many flowers 

 there is a single pistil, which appears to be formed from a 

 single leaf -like structure known as a 



carpel. If we imagine a small nar- 



row leaf with one or more ovules 



attached on its margin, and then this 



leaf rolled so as to bring its edges to- 



gether and the ovules inside the in- 



closed cavity, the formation of a 



simple pistil from a carpel would be 



illustrated. 



In buttercups there are many 



simple pistils in a flower. In very 



many flowers the pistils have united 



together to form a compound pistil. 



In some of these the ovaries of the 



pistils are more or less united, but 



there are as many styles as there were pistils (Fig. 64, A and 



B). In others there is complete union so that there is one 



ovary and one style (Fig. 64, (7), and only careful examina- 

 tion of grooves on the surface and of 

 sections shows that the pistil is com- 

 pounded of two or more simple pistils. 

 Fig. 65, A, B, shows in cross section 

 two kinds of ovaries formed from 

 three carpels. In A the carpels ap- 

 pear to have united at the edges, 

 Caving a single cavity in the ovary 

 and the ovules attached to the outer 

 wal j . while in t h e arrangement 



. . . . 



suggests that three simple pistils 

 have united completely, so that the ovules are attached to 

 a central column. 



200. Irregular Flowers. In the bean flower we have 

 already studied a good example of irregular flowers; that is, 



FIG. 65. Transverse sec- 

 tions of two ovaries, 



with one chamber and in 

 B with three chambers. 



w, ovary wall. 



