HOW PLANTS MARRY. 91 



do actually so fertilise themselves with their 

 own pollen. But such flowers are almost always 

 poor and degenerate kinds, the unsuccessful in 

 the race, the outcasts and street arabs of plant 

 civilisation. All the higher, nobler, and more 

 dominant plants — the plants that have carved 

 out for themselves great careers in the world, 

 and that occupy the best posts in nature — have 

 invented some mode or other of cross-fertilisa- 

 Hon, as it is called, that is to say some plan by 

 which the pollen of one plant or flower fertilises 

 the pistil of another. 



What does this mean? Well, regarding the 

 plant as a colony, you will see at once that the 

 stamens and pistil of the same blossom stand to 

 one another somewhat in the relation of brothers 

 and sisters, while those of different flowers on the 

 same plant may ba regarded at least in the light 

 of first cousins. Now the very same thing that 

 makes sex and marriage desirable, makes close 

 intermarriage of blood relations undesirable. 

 ** Marrying in and in," as it is called, tends to 

 produce weak and feeble offspring, while *'an 

 infusion of fresh blood" tends to make botli 

 plants and animals stronger and more vigorous. 

 Hence, if any habit chanced to arise in plants 

 which favoured or rendered easier such cross- 

 fertilisation, it would result in stronger and more 

 vigorous young, and would therefore be fixed by 

 natural selection. The actual consequence is 

 that in the world of plants, as we see it to-day, 

 every great dominant or successful race has 

 invented some means of cross-fertilisation, either 

 by the agency of wind or of insects, while only 



