346 NATURE STUDY AND AGRICULTURE 



the female gametophyte and the formation of the eggs; for 

 the female gametophyte, instead of developing outward 

 and into an independent plant, as its forerunners did, will 

 develop inward and live as a parasite upon its mother, the 

 megaspore. The sporophyte began by being dependent 

 upon the gametophyte, and now the gametophyte in turn 

 has become dependent upon the sporophyte. 



The group of plants next higher than the fern plants is 

 the highest of all and is commonly known as the " flowering 

 plants," but it is better called the "seed plants." (There 

 are some seed plants which could hardly be said to be 

 flower bearers.) To understand this group one must 

 carry forward the ideas of strobilus and heterospory and 

 see how they result in flower and seed. 



Among seed plants the strobilus continues for a long 

 time, notably so in the group to which the pines belong. 

 Finally a third type of leaflike structure appears and this 

 new member is close to the sporophylls. Presently we see 

 this new organ itself differentiated into two kinds, and these 

 are called sepals and petals, which are the most familiar 

 parts of a flower. Thus we may say that when a strobilus 

 has sepals and petals associated with its sporophylls it is a 

 flower. We must note that the sporophylls of a flower 

 were called stamens and carpels or pistils long before their 

 real nature was understood, and these names still persist. 

 It used to be thought that stamens were male organs and 

 the pistil the female organ, and plants which have stamens 

 on one individual and pistils in the flowers of another gave 

 rise to the idea of distinct male and female plants. But, 

 if the argument has been followed up to this point, the 

 inaccuracy of this view is perfectly obvious. The stamens 



