58 REPRODUCTION 



IS true, however, that plants, like animals, do have in their 

 life history a reduction in the number of chromosomes 

 which compensates for the doubling of this number that 

 occurs when sperm and egg fuse. 



Plants differ from animals in having what is called 

 alternation of generations, a phenomenon described in a 

 later chapter. One of these generations (gametophyte) 

 bears gametes, the other (sporophyte) bears spores, and 

 the two together complete the life cycle of the plant. 

 The reduction division occurs in connection with the 

 formation of the spores. 



9. Sex in the Offspring. The differences between the 

 eggs and sperms are not just occasional, exceptional 

 facts. They are very constant differences in the plant and 

 animal kingdoms. Animals and plants regularly produce 

 two kinds of offspring, eggs and sperms; usually neither of 

 these can develop alone; they unite into one individual, 

 and this individual has all the powers of the species. These 

 differences in the gametes are differences of sex. They 

 are the most fundamental differences in sex. The qggs 

 and sperms are the "sex-cells." The egg is a female cell, 

 or offspring; the sperm is a male offspring. Fertilization 

 produces a new individual made up of the two kinds of cells. 



