SEXUAL REPRODUCTION. l ^ l 



to Median's protest (see pp. 71, 72), that self-fertilization is neither 

 so rare nor so ' ' abhorrent " as is now generally believed. 



In a great number of cases cross-fertilization by means of insects 

 does occur; in many it must occur. In another by no means small 

 set of flowering plants — usually with inconspicuous blossoms — the 

 fertilizing golddust is borne by the wind, and falls, like the golden 

 shower on Danae, upon adjacent flowers. In many hermaphrodite 

 flowers, again, self-fertilization does certainly take place; in some this 

 is necessarily so. Interesting in this connection is the indubitable 

 self-fertilization which occurs in the small degenerate unopening 

 (cleistogamous) flowers of some plants, such as species of balsam, 

 deadnettle, pansy, &c. These occur along with ordinary flowers, 

 and, curiously enough, are sometimes more fertile than they. 



Fig. 41. — Bees visiting White Deadnettle and Broom. 



In most of the lower plants the male elements are minute and 

 actively mobile. They find their way through the water, or along 

 capillary spaces between the leaves, to the passive female cells. In 

 some cases there is a curvature of the male organ toward an adjacent 

 female organ, apparently in obedience to chemical or physical attrac- 

 tion. Even here close fertilization seems exceptional, and is often 

 impossible. 



So far, however, only the external aspect of the process. As 

 long ago as 1694 Camerarius showed that if the male flowers of hemp, 

 maize, and other plants were removed, the female flowers bore no 

 seeds, or at least no fertile ones. In 1704 E. F. Geoffroy castrated 

 certain plants by removing the stamens and noted that they remained 

 barren. " Mirandum sane," he wrote, " quam similem servet natura 

 cunctis in viventibus generandis harmoniam." Reasonable as this 

 now appears to us, the fundamental fact was not only slowly recog- 

 nized, but on into the present century there was found naturalists 



