KEPliODUCTlON IN PLANTS AND ANIMALS 277 



quite dissimilar to that of the animals. The flower (fig. 128) is 

 the reproductive organ in seed plants. It consists of four dis- 

 tinctly different kinds of structures ; some of these structures 

 may be absent. In a complete flower the lowest floral organs 

 are the sepals (fig. 129), collectively known as the calyx; 

 next above the sepals are the petals, collectively known as the 

 corolla; above the petals are the stamens, and above the sta- 

 mens, the pistils. In the flowers of some plants the pistils are 

 absent and the flowers are said to be staminate ; if the sta- 

 mens are absent the flowers are pistilate. Sometimes pistilate 

 flowers are borne on some" 

 of the branches of a plant 

 and staminate flowers on 

 other branches. 



304. The pistil. Careful 

 observation of the pistil 

 will ordinarily show that 

 there is a swollen basal 

 portion known as the ovary, 

 above which is a more elon- 

 gated part, the style, and 

 above that the tip portion, 

 known as the stigma. By 

 opening the ovary we may 

 find within it small bodies, 



the ovules (fig. 130), which when mature are the seeds. When 

 we take a very thin section of a young ovule and examine it 

 under the microscope, we see that in its center there is an elon- 

 gated sac, the embryo sac. At one end of the embryo sac the egg 

 cell is formed. Eggs, therefore, may be found in the flowering 

 plant just as truly as in animals, but these eggs remain in- 

 closed within the ovary and are not set free as in the frog. 



305. The stamen. The swollen tip of the stamen is the 

 anther. Within the anther there are many small cells, the pol- 

 len grains, which, when the anthers break open, are scattered 



stamen 



N 



^ 2- pistil 



FIG. 129. Diagram of flower, showing 

 the different parts 



