THE COMPOUND PISTIL. 



301 



(Ord. Asclepiadacese and Apocynacese). Numerous illustrations 

 of ali the varied forms are 

 given in the systematic part 

 of this volume. The an- 

 nexed diagrams represent, 

 Fig. 378, 379, three dis- 

 tinct but approximated pis- 

 tils ; Fig. 380, 381, three 

 pistils with their ovaries 

 coalescent; and Fig. 382, 

 383, three pistils with their 

 styles as well as their ova- 

 ries united into one. 



546. The Compound Pistil, 



From these illustrations the regular structure of the compound 

 pistil is readily seen, at least as to the more common and normal 

 case, namely, where the cross-section displays two or more cells, 

 or separate cavities. For it is evident that, if the contiguous parts 

 of a whorl of three or more carpels cohere, the resulting compound 

 ovary will have as many cavities, or cells, as there are carpels in 

 its composition, and the placentae will all be brought together in 

 the axis ; as is shown in Fig. 381, 383, in Fig. 291, and in the gy- 

 na3cium of Fig. 306, as compared with Fig. 284, &c. 



547. The partitions, or DISSEPIMENTS, which divide the com- 

 pound ovary into cells, are evidently composed of the united con- 

 tiguous portions of the walls of the carpels. These necessarily 

 consist of two layers, one belonging to each carpel ; they are 

 always vertical, and are equal in number to the carpels of which 

 the compound pistil is constructed. 



548. A single carpel, therefore, has no proper dissepiment. It 

 is, however, sometimes divided by spurious partitions, separating 

 the cavity into separate cells or joints, placed one above another, 

 as in some species of Cassia, in Desmodium, &c. (Fig. 440, 441) ; 

 or even by a vertical false dissepiment produced by the introflex- 

 ion of the inner or placental suture, as is partially the case in some 

 species of Phaca and Oxytropis (Fig. 445) ; or by a projection 



FIG. 378. A whorl of three pistils, the line which passes down the inner side representing 

 the ventral suture. 379. A cross-section of their ovaries, showing the two rows of ovules, oc- 

 cupying the inner angle, or ventral suture. 380. A whorl of three pistils, their ovaries united. 

 331. A cross-section of the same. 382. Three pistils, with their styles also united quite to the 

 summit. 333. A cross-section of the united ovaries. 



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