52 ORGANOGRAPHY. 



the ovary; and the stigma (Fig. 126, dig), the more or 

 less enlarged upper end of the style. The style may be 

 wanting, which renders the stigma sessile. According as 

 the pistil, or carpel, as it is sometimes called, is formed of 

 a single leaf or of several leaves, it is simple or compound. 

 In a simple pistil, formed by a single leaf folded edge to 

 edge, the seeds are borne on the part of the inner wall, 

 which corresponds to the line of union of the edges, and is 

 called the placenta (Fig. 126, pla). If two placentae are 

 present, they must have resulted from the union of two 

 leaves, edge to edge ; if three placentae, from the union of 

 three leaves, etc. Therefore the presence of two or more 

 placentae is proof of a compound pistil. The number of 



styles generally corresponds to 

 the number of leaves entering 

 into the formation of the carpel. 

 65. Compound pistils may 

 '^^ 12s have a single cell, or they may 



Lave many cells. When the latter have simply united 

 with each other, edge to edge (Fig. 127), there will be but 

 one cell, and the placentae, or seed-bearing lines, will be 

 situated on the ovary wall, as in the simple pistil ; that is, 

 they will be parietal {Ij&t. paries, wall). If each separate 

 carpellary leaf unites edge to edge, and then all the carpels 

 join (Fig. 128), the ovary will have as many cells as there 

 were carpellary leaves, the seed-bearing lines will be 

 crowded to the centre and form central placentae. The 

 dissepiments or walls which separate the cells from one 

 another may become obliterated, leaving the seed-bearing 

 column in the centre of a continuous or one-celled cavity, 



Figs. 127, 128. Diagrammatic sections of compound ovaries : 127. One-celled ovary 

 parietal placenta ; 128. Many-ceUed ovary, placentae central. ' 



