LESSON 18.] 



SIMPLE PISTILS. 



117 



simple or compound. A simple pistil answers to a single leaf. A 

 compound pistil answers to two or more leaves combined, just as a 

 monopetalous corolla (263) answers to two or more petals, or leaves 

 of the flower, united into one body. In theory, accordingly, 



305. The Simple Pistil, OF Carpel (as it is sometimes called), consists 

 of the blade of a leaf, curved until the margins meet and unite, form- 

 ing in this way a closed case or pod, which is the ovary. So that 

 the upper face of the altered leaf answers to the inner surface of the 

 ovary, and the lower, to its outer surface. And the ovules are borne 

 on whut answers to the united edges of the leaf. The tapering sum- 

 mit, rolled together and prolonged, forms the style, when there is 

 any ; and the edges of the altered leaf turned outwards, either at 

 the tip or along the inner side of the style, form the stigma. To 

 make this perfectly clear, compare a leaf folded together in this way 

 (as m Fig. 2.31) with a pistil of a 



Garden Pieony, or Larkspur, or with 

 that in Fig. 252 ; or, later in the 

 season, notice how these, as ripe pods, 

 split down along the line formed by 

 the united edges, and open out again 

 into a sort of leaf, as in the Marsh- 

 Marigold (Fig. 253). In the Double- 

 flowering Cherry the pistil occasion 

 ally is found changed back again into 

 a small green leaf, partly folded, much as in Fig. 251. 



306. Fig. 172 represents a simple pistil on a larger scale, the. 

 ovary cut through to show how the ovules (when numerous) are 

 attached to what answers to the two margins of the leaf. The 

 Stonecrop (Fig. 168) has five such pistils in a circle, each with the 

 side where the ovules are attached turned to the centre of the flower. 



307. The line or seam down the inner side, which answers to the 

 united edges of the leaf, and bears the ovules, is called the ventral or 

 inner Suture. A corresponding line down the back of the ovary, 

 and which answers to the middle of the leaf, is named the dorsal or 

 outer Suture. 



308. The ventral suture inside, where it projects a little into the 



253 



FIG. 251. A leaf rolled up inwards, to show how the pistil is supposed to he formed. 



FIG. 252. Pistil of Isopyrum biternatuin cut across, witli the inner suture turned towards 

 the eye. 



FIG. 253. Pod or ripe pistil of the Caltha, or Marsh-Marigold, after opening. 



