THE FLOWER 



85 



attaclied at their margins may form a pistil of only one ckamber, 

 but if tke margins are rolled inward, uniting at the center, there 

 will be two or three or more chambers corresponding to the 

 number of carpels. The point of attachment of the oviiles is 

 known as the placenta, which may be parietal, if on the side, or 

 central, if in the central axisi, or free central, if on a free column 

 arising from the center (Fig. 64). The size and number of the 



Fig. 64. — Types of ovaries; (o) and (6) one carpel, one chamber, central placenta; (c) 

 one carpel, one chamber, parietal placentse; (d) two carpels, two chambers, central placenta; 

 (e) three carpels, three chambers, central placenta; (/) one chamber, three carpels, parietal 

 placenta. 



ovrdes vary greatly in diiferent species of plants. The parts of 



the ovule will be taken up in the next chapter. 



The stamens and pistils constitute the essential organs of 



the plant. They are, in a sense, the reproductive organs of the 



plant and are necessary for seed production. A flower to be 



functional must possess one or the other or both of these organs. 



The processes of reproduction will be discussed in the 



next chapter.* 



* The siffnificance of the terms micro sporophyll, macrosporophyll, 

 Tnicrosporangium, macrosporangium, and microspore will be explained in 

 Chapters XXVI-XXVIII. 



