100 Principles of Plant Culture. 



(23). Cross-pollination is often performed artificially 

 ,(440). 



Close- or self-pollination occurs when the stigma receives 

 pollen from its own flower or plant. 



153. Cross-Pollination is Advantageous in plants, as 

 Darwin's careful experiments have shown. The seeds 

 -formed are usually more numerous and larger and make 

 more vigorous plants than with close-pollination. Es- 

 pecially is this true when the parent plants have been 

 subjected to different growth conditions in previous gen- 

 erations. Nature favors cross-pollination in perfect- 

 flowered plants by numerous adaptations tending to pre- 

 vent self-pollination, as maturing the p(jl]en either before 

 or after the receptixe stage of the stigma, or so locating 

 the stamens that the pollen is not readily deposited on 

 the stigma of the same flower.* In some cases, pollen 

 is infertile on a stigma of the same flower or plant that 

 is abundantly fertile on stigmas of other plants of the 

 same species (155). 



154. Perfect, Monoecious (mo noe'-cious) and Dicecious 

 (di-ce'-cious) Flowers. Flowers containing both stamens 

 and pistils (or pistil), as in the apple, tomato, cabbage 

 etc., are called perfect or hermaphrodite (her-maph'-ro- 

 dite) ; those containing but one of these organs, as in the 

 melon, Indian corn etc., are called imperfect or unisexual 

 (u'-ni-sex'-u-al).t Flowers of the latter class are called 

 monoecious when the stamen-bearing (staminate (stam'-i- 



* Darwin's work " On the Various Contrivances by wtiich Orcliids are 

 Fertilized by Insects " describes many most interesting adaptations of 

 this sort. 



t The terms hermaphrodite, unisexual and bisexual, though often ap- 

 plied to flowers, are inaccurate. 



