42 THE FLOWER. 



axis, while the lower surface becomes the outer. By this arrangement the two 

 edges of the carpel often appear like swfMres (Lat. sutura, a seam), of which the 

 outer, formed by the midvein, is called the dorsal, and the inner, formed by the 

 nnited margins, the ventral. 



a. This view of the pistil is remarkably confirmed and illustrated by the flowers 

 of the double cherry, where the pistil may be seen in every degree of transition, 

 reverting towards the form of the leaf. This carpellary leaf {Fig. 10 ; 9) stands in 

 the place of the pistil, having the edges infolded towards each other, the midvein 

 greatly prolonged, and a little dilated at the apex. 



h. If this be compared with the pistil of the cherr}% seen in the figure, no doubt 

 can be entertained that the two sides of the leaf correspond to the walls of the 

 ovary, the margins to the ventral suture, the midvein to the dorsal suture, and 

 the lengthened summit of the leaf to the style and stigma. Sometimes the 

 flower contains two such leaves, which always present their concave faces towards 

 each other, as seen in the figure. This corresponds with the position of the true 

 carpels, in which the ventral sutures of each are contiguous. 



c. Many other plants, as the rose, Anemone, Ranunculus, &c. exhibit similar 

 transformations of the pistil, so that there can be no doubt that the carpel is 

 formed upon the same plan in all plants. The ovary, therefore, is the blade of a 

 leaf; the style, the lengthened apex ; and the stigma, a thickened and denuded portion 

 of the. upper margin of the leaf 



85. From this doctrine of the structure of the single carpel, 

 the student will be able and expected to demonstrate many 

 propositions Hke the following. 



a. First. A compound ovary consists of a whorl of carpellaiy 

 leaves, their united edges all meeting in the centre, and the 

 cohering sides forming a kind of radiation from it (Fig. 9). 



h. Second. There must be as many cells as there are carpels. 



c. Third. The partitions between the cells, that is, the dis- 

 sepiments {dissepio, to separate,) must each be double; they 

 must be vertical ; they must be equal in number to the carpels, 

 and alternate with the stigma, which is also double. 



d. Again, the single carpel can have no true dissepiment. If 

 any ever occur, it is regarded as an anomaly, and called spurious. 

 Ex. flax (Fig. 11). 



86. These propositions are true only when each carpellaiy 

 leaf appears in its normal condition, that is, with its tw^o edges 

 mutually united. But cases occur where only the margins of 

 adjacent leaves are united (Fig. 11 ; 1, 2, 3). In this case there 

 will be no dissepiments, and the compound ovary ^vill, of course, 

 become one-celled. Ex. Primula, Gentiana. 



