THE PISTILS, OR GTNECIUM. 



107 



525. Two MODES OF COHESIOX in the carpellary circle greatly affect 

 the structure of the ovary and fruit. First and regularly, the carpels 

 may be closed as when simple, and conjoined by their sides and fronts, 

 as in lily and marsh mallow. In this case, 



1, The compound ovary will have as many cells as carpels. 



2, The partitions between the cells, i. e., the dissepiments (dissepio, 

 to separate) will each be double, will meet in the center, will be verti- 

 cal and alternate with the stigmas. 



3, The single carpel can have no true dissepiment. If any ever 

 occur it is regarded as spurious, being a membranous expansion of the 

 dorsal suture or the placentae, as in flax. 



4, The placentae as well as the ventral suture will be arial, and the 

 dorsal suture on the outer wall, opposite the stigmas. 



526. AGAIN, the carpels may each be open and conjoined ,by their 

 edges, as the petals in a monopetalous corolla. So it is in the com- 

 pound ovary of the violet, rock-rose. In this case, 



1, There will be no dissepiment (unless spurious, as ia the Cruciferae), 

 and but one cell. 



2, The placentae of each carpel will be separated and carried back 

 to the wall of the ovary, i. e., they will become parietal (paries, 

 a wall.) 



527. INTERMEDIATE CONDITIONS. Between the two conditions of axilc (or cen- 

 tral) and parietal placentae we find all degrees of transition, as illustrated ia the 

 different species of St. John'swort, and in poppy, where the inflected margins of 



the carpels carry the placentae inward, well 

 nigh to the axis. Moreover, the plaeentae 

 are not always mere marginal lines- but 



394 895 396 S9T 



897, Flower of Dodecatheon Meadia. 394, Vertical section showing the free central placenta. 

 895, Vertical section of Lucojum (Snow-flake). 396, Cross section of ovary. 



