100 Principles of Plant Culture. 



(23). Cross- poll ination is often performed artificially 

 (440). 



Close- or self-pollination occurs when the stigina 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 pollen either before 

 or after the receptive 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-no3'-cious) and Dioecious 

 (di-re'-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 which Orchids 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. 



