How Plants Perpetuate Their Kinds 291 



sexual structures, is taken in the flowering plants, which carry 

 their sexual parts high up in the air. In consequence of the greater 

 dryness of that situation, they have had to bury their sexual parts 

 far more deeply (viz., deep inside the ovules and anthers), and 

 have had to abandon the free-swimming sperm cell of all the 

 lower kinds and replace it by the growing pollen-tube, which 

 carries the male cell to the female cell in the way we have already 

 described. In a word, the structures developed adaptively in re- 

 sponse to the conditions of protection and fertilization in these 

 highest plants are the stamens and pistils, the essential parts of the 

 flower which we have already described. But all such structures, 

 like all of the sexual parts and adaptations developed by animals, 

 are in reality secondary, being merely arrangements to enable the 

 male cell to effect fertilization and the female cell to receive it. 

 The central and essential feature of fertilization and sexual union, 

 viz., the union of nuclei carrying the hereditary qualities of two 

 parents ; and the central and essential feature of difference between 

 the sexes, viz., a division of labor between the two parents; 

 these remain the same throughout the plant and animal kingdoms 

 from the lowliest of the seaweeds up to man himself. 



Sex, therefore, does not arise in any essential difference of rela- 

 tion of the two parents to offspring, but in a minor and mechanical 

 matter of division of labor between the sexual cells, involving 

 secondary differences in various accessory structures. Sex, so to 

 speak, is not a matter of method but of mechanism, and exists not 

 for the sake of the formation of offspring but for giving it a more 

 certain and better start in its life. That cell, structure, or in- 

 dividual, which is devoted to nourishing and protecting the young 

 individual formed as a result of fertilization we call female: that 

 cell, structure, or individual, which is devoted to bringing the two 

 cells together for fertilization we call male. This difference is the 

 central feature of all the phenomena of sex, although worked out 

 with infinite variety of detail and more or less interlocked with 

 other considerations; and it explains not only sexual structures in 



