STRUCTURE.] ANOMALOUS PLACENTA. 375 



uppermost ; a circumstance that leads to no intricacy of struc- 

 ture when the carpels are distinct, but which may cause an 

 exceedingly anomalous structure in syncarpous pistils, espe- 

 cially when accompanied by other unusual modifications. 



125 126 



There can be no doubt that the true nature of the com- 

 position of the pomegranate is to be explained upon this 

 principle. In order to make these considerations more clear, 

 let figs. 125, 126, and 127. represent fig. 125. a convex 

 receptacle, with distinct carpels ; fig. 126. a concave one, with 

 the same; and fig. 127. a concave one, with the carpels con- 

 solidated. In these, a a are the outer row of carpels, b b the 

 next, and d d the central row. The relative position of 

 these, as the receptacle is convex or concave, will now be 

 apparent. 



I have stated that the placenta, however simple it may 

 appear to be, is usually produced by the union of two united 

 margins of a carpellary leaf: it is, therefore, essentially 

 double; and, accordingly, we find that in polyspermous 

 ovaries the ovules are almost always arranged in two rows, 

 as in the Pea and Bean, the Quince, the Pseony, &c. 



But there are exceptions to this rule. In Taylor's Maga- 

 zine for Nov., 1837, I have shown that in Broomrapes 

 (Orobanchacese) the placentae undoubtedly arise from the 

 face of the carpel. That the capsule of such plants consists 

 of two carpels standing right and left of the axis of inflo- 

 rescence, and with the margins not inflected in the form of 

 dissepiments, is incontestable. Yet in Orobanche and Phely- 

 psea the capsule has the placentae placed equi-distant in pairs 

 upon the face of each valve or carpel, and considerably 



