REPRODUCTION 187 



but upon its under surface there eventually appear two 

 groups of sexual organs, antheridia, constituting the male 

 elements and producing spermatozoids; and archegonia, 

 or female elements, producing each a single egg cell or 

 ovum. Water is essential to the further progress of 

 events, in order that the spermatozoids, which swim 

 freely, may reach the archegonia, to which they are at- 

 tracted through a chemotropic affinity, that probably de- 

 pends upon the presence of malic acid in the latter. 

 Reaching the ovum in the archegonium a spermatozoid 

 conjugates with it, after which the fertilized ovum devel- 

 ops into the asexual plant or fern. Here we find an alter- 

 nation of generations, the purpose of which seems to be 

 conjugation, though how such conjugation of two cells 

 directly traceable to a common parent can be so essen- 

 tial as to merit so roundabout a method for its accom- 

 plishment is difficult to imagine. 



The reproduction of the higher plants shows many 

 interesting endeavors to escape " self-fertilization " and 

 profit by the advantages of "cross-fertilization," though 

 the latter can scarcely be said to assume the importance 

 that is seen among animals. 



Thus, among the phanerogams, or flowering plants, we 

 find many plants bearing flowers possessing male (anthers) 

 and female (pistil) organs that mature at the same time, 

 so that their fertilization must usually be affected 

 by their own pollen grains dropping directly upon the 

 stigma, growing down to the ovules in the ovary, con- 

 jugating with and fertilizing them. Indeed, in cleistoga- 

 mous flowers, like the peas, in which the sexual organs 

 are never exposed, it is scarcely possible for fertilization 

 to take place in any other way. But although this is 

 characteristic of a number of plants, so many devices 

 are found among flowers in general, for its prevention, 

 that it would seem as though the best interest of plant 

 life is opposed to it. Thus the stigma and anthers of 

 flowers do not usually mature at the same time; i.e., they 

 are subject to protandry, or the maturation of the an- 



