294 The Living Plant 



of seed propagation; and whenever they have obtained a specially 

 good kind, they try to preserve it by propagating it asexually. 

 But we are verging over to the subject of plant breeding, which 

 is a matter so important that it must later receive a chapter to 

 itself. 



We must here turn back to fertilization in order to consider 

 another important phenomenon in connection therewith. Al- 

 though in the higher plants both pistils and stamens are usually 

 associated closely together within one flower, it is only excep- 

 tionally the case that egg-cells are fertilized by pollen from that 

 same flower. On the contrary there exist the most elaborate ar- 

 rangements adapted to prevent such a close fertilization, and 

 ensure that the sex cells which unite shall come from different 

 flowers, and usually indeed from different plants. It is in adapta- 

 tion to such cross pollination that plants have developed the more 

 conspicuous features of the flower, the nectar, odor and showy 

 corolla in particular, as will appear in the following chapter which 

 is wholly devoted to this interesting subject. Indeed, in some 

 plants the arrangement is such, notably where the stamens and 

 pistils are borne on quite different plants, that close fertilization 

 is not even possible ; and this arrangement is universal among the 

 higher animals. Now it is quite plain that the fertilization of an 

 ovule by pollen from the very same flower would be vastly easier 

 of accomplishment than is the elaborate cross fertilization, — re- 

 quiring no more, indeed, that a simple turning of the stamen over 

 against the stigma, when the growth of the pollen-tube would 

 accomplish the rest; and the fact that plants not only choose the 

 most difficult method, but also even abandon in the higher forms 

 the very possibility of the simpler, shows quite conclusively that 

 cross fertilization has some great merit above close fertilization. 

 And the reason for the superiority is not difficult to find. It was 

 first indicated by the experiments of Darwin, who showed that 

 the progeny resulting from cross fertihzation can be more vigorous 

 and numerous than those from close fertilization; and the same 



