THE FLOWER 



85 



attached at their margins may form a pistil of only one chamber, 

 but if the 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 ovules is 

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

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

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



Fia. 64. Types of ovaries; (a) and (6) one carpel, one chamber, central placenta; (c) 

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

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

 placenta. 



ovules vary greatly in different 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 significance of the terms microsporophyll, macrosporophyll, 

 microsporanyium, macrosporangium, and microstore will be explained in 

 Chapters XXVI-XXVIII. 



