VII.] 



THE PISTIL. 



79 



to the carpels which bear them, and that they all radiate, 

 as it were, from the centre of the flower. A like obliquity 

 may be noticed in the Pea and Bean, the single carpel 

 which these possess being the only one developed of 

 a whorl of five. Sometimes one or more of the carpels 

 suppressed in the Pea and Bean are developed in other 

 species which are allied to them in general structure. 



But Larkspur, Monkshood, or Columbine, furnish good 

 connecting links between the Buttercup and the Pea ; for 

 in these plants you find the carpels 

 larger than in Buttercup, but fewer in 

 number, varying from one to five, 

 and standing in a whorl around the 

 centre of the flower. Each carpel of 

 the pistil of either of these three 

 plants answers to the pistil, consist- 

 ing of one carpel, of the Pea and 

 Bean. In all of these plants the pistil 

 is apocarpous ; the carpels, however, 

 differ in number, as well as in the 

 number of ovules which they contain, 

 and in their mode of opening when 

 ripe (dehiscence) to allow the seeds to 

 escape. 



Observe that in Larkspur, Monks- 

 hood, and Columbine, the ovules and 

 seeds are borne upon the inner angle 

 of the carpels. The same in Pea and 

 Bean; and the inner angle of the 

 carpels coincides with the axis of the flower. 



Now ovules are, as a general rule, marginal buds (the 

 nature and relation of which, to ordinary leaf-buds, is 

 still a matter for investigation), that is, they are borne, 

 obviously, in a large proportion of cases, upon the 

 margins of carpellary leaves ; hence we may regard the 

 inner angle of each carpel, upon which the seeds are 

 arranged, as answering to the line of union of its infolded 

 edges. This line is called the ventral suture. 



To take the Pea again as the simplest case : if you split 

 it carefully open up the edge bearing the seeds, you will 

 find, when laid open, that half of the seeds are on one 

 edge, half on the other, each margin being alternately 



FIG. 52. Fruit-carpels 

 {follicles) of Colum- 

 bine. The front ones 

 cut across to show 

 the attachment of the 

 seeds to the ventral 

 sutures. 



