PISTIL. 



81 



Fig. 131. 



carpels are united without being inflected much, if at all, as in 

 the Corydalis and Viola (Fig. 130), where the placenta is said 

 to be parietal. In the other case the dissepiments exist in the 

 very early stage of the ovary, but by the enlargement of the 

 ovary without the corresponding development of the dissepi- 

 ments, they become torn and obliterated, with the placenta re- 

 maining alone, as in the Cerastium. In this case it is called a 

 free central placenta. (Fig. 131.) 



It is frequently the case that there are 

 numerous carpels, but they contract no 

 union with each other, as in the Straw- 

 berry, Ranunculus, and Anemone. 



When the carpels are united, as in the 

 Poppy, Hibiscus, <fec, they are said to be 

 st/ncarpous. When they are free, as in 

 the Ranunculus, Strawberry, <fec, they are 

 called apocarpous. 



133. From the fact that the pistil consists of a whorl of leaves 

 immediately superior to those composing the stamens, it follows 

 that the leaves of the whorls should be alternate with each other ; 

 and this is their position in cases in which we are able to de- 

 termine in regard to it. 



Central placenta. 



Fig. 132. 



Fig. 133. 



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Arrangement of stamens and carpels. 



Two whorls of carpels. 



If in Fig. 132, a, a, a, a, a, represent five stamens, and b, b, 

 as many carpels, it will be observed that the stamens occupy 

 alternate positions in respect to the carpels. This is undoubtedly 

 the fact in all cases which are not altered by non-development 

 or unusual modifications. When the carpels consist of several 

 whorls on the same plane, the individuals of contiguous whorls 



"What is a parietal placenta? A free central placenta? What is a syn- 

 carpoub fruit ? What apocarpous ?— 133. How are the carpels arranged • 



4* 



