So 



THE PISTIL. 



[CHAP. 



seed-bearing. Up the middle of the opened carpel you 

 have a strong line or nerve (the outer angle when the 

 carpel was closed), which is, simply, the midrib of the 

 carpellary leaf, answering to the midrib which we find in 

 foliage-leaves. This line is called the dorsal suture. 



The apex of the carpel is continued into the short 

 style, and terminates in the stigma, which withers before 

 the Pea is ripe. Each of the carpels in the other plants 

 which we have just examined presents the same features 

 as the Pea. The Buttercup differs only in the small size 

 of the carpels, each adapted to contain one small seed. 



Suppose, now, the 5 carpels of the pistil of Columbine, 

 instead of being free from each other, had been developed 

 cohering to each other by their inner faces. The conse- 

 quence would have been that we should have had a 

 syncarpous pistil with a 5-celled ovary. And syncarpous 

 pistils with 5 cells, or more than 5 cells (as Orange), or 

 fewer than 5 (as Tulip), occur on every hand, and are 

 nearly always explicable in this way; that is, by the 

 cohesion of as many carpels as there are cells in the 

 syncarpous ovary. It follows from this explanation of 



FIG. 53. Transverse section of the FIG. 54. Transverse section of the 

 3 celled ovary of Tulip, shewing 2 -celled ovary of Foxglove, show- 



axile placentation. ing axile placentation. 



the structure of a syncarpous ovary that each of the 

 divisions, called dissepiments, by which syncarpous 

 ovaries are separated into distinct cells, must be double. 

 They must each necessarily consist of the two infolded 

 and cohering sides of adjacent carpels. And so we often 

 find that when syncarpous pistils are ripe, their carpels 

 separate from each other, each dissepiment splitting into 

 two plates. 



