88 



THE SECOND BOOK OF BOTANY. 



part of the carpel. Fold in the margins slightly to 

 represent the placentae (Fig. 164). (See " First Book," 

 Ex. LXVIII.) If the fold will not stay in place, take 

 a stitch or two along it with a needle and thread. Now 

 double it at the midrib (Fig. 165), and compare it 

 with a pea-pod. Find the valves; the dorsal and 

 ventral portions ; the stigma ; the base. 



FIG. 164. 



FIG. 165. 



Gather some old, faded pea-blossoms, in which 

 the ovary is somewhat enlarged, and observe that the 

 ventral suture is turned inward ; that is, it lies along 

 the central line, or axis, of the flower. It is along 

 this axis, then, that the double placentae are formed. 

 Observe the position of the dorsal suture, or back of 

 the pod. It is important to bear in mind that, in the 

 case of the simple pistil, the ovules are attached cen- 

 trally along the axis of the flower. 



