THE CYCLE OF LIFE : FLOWERS 



43 



34. The ovary. If you cut open the ovary in any flower, you 

 will find that it consists of a hollow box, with several compart- 

 ments in some species, corresponding to the carpels (see Fig. i8). 

 This hollow box contains from one to very many of the tiny 

 ovules, each of which may become a seed. As time goes on these 

 ovules enlarge and the ovary also becomes larger. By the time 

 the seeds are ripe the ovary has become the jruit. In the mean- 

 time the corolla 

 and the calyx, as 

 well as the sta- 

 mens, have fallen 

 off or shriveled 

 away in most cases, 

 so that most peo- 

 ple never discover 

 for themselves that 

 one has anything 

 to do with the 

 other. 



But the chang- 

 ing of ovules into 

 seeds is not simply 

 a matter of growth. Every farmer and gardener knows that 

 it is possible to have plenty of flowers or blossoms with a very 

 poor crop of fruit, even when the conditions for growth are of 

 the best, and even though the plants are perfectly healthy. 



35. Fertilization. Farmers and orchaidists have known for 

 many centuries that flowers will remain sterile (that is, they 

 will fail to produce seed) unless some of the powdery pollen 

 (/, Fig. 17) from the stamen somehow gets onto the stigma. 

 This transfer of pollen was accordingly called fertilization, the 

 idea being that the pollen makes the pistil jertile, or capable of 

 bearing seed. But less than a hundred years ago the real facts 

 about seed-making were discovered. When the pollen grain gets 

 to the stigma, it absorbs some of the sirupy fluid on the latter. 

 Then there begins to grow out of it a very thin thread, or tube, 



Fig. 18. Sections of ovaries 



Ovaries are of many sizes and shapes. They contain but 

 a single ovule in some species of plants, and in other 

 species they bear hundreds. The ovules are definitely 

 placed in one or more compartments of the ovary. Each 

 compartment, with its style and stigma, is sometimes 



called a carpel 



