CHAP. II. 



OVARY. 



171 



single whorl of parts, so the pistil is more frequently com- 

 posed of one whorl of carpels than of more. There are, how- 

 ever, certain families in which several whorls are produced 

 one within the other, as in Fragaria, Ranunculus, Magnolia, 

 Annona, and the like. In these cases it mostly happens that 

 the carpels are either entirely separate or nearly so ; but it 

 sometimes happens that syncarpous pistils are habitually pro- 

 duced with more than one whorl of carpels, and consequently 

 of cells, as Nicotiana multivalvis, and some varieties of the 

 genus Citrus. In such instances the placentae of the outer 

 series will necessarily be applied to the backs of the inner 

 series, as has been just demonstrated. 



This mutual relation of the different rows of carpels is 

 sometimes observed when the I'eceptacle from which they 

 arise is either convex or concave: in the former state the 

 outer series will obviously be lowermost, and in the latter 

 uppermost; a circumstance tha't 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 of 

 structure. There can be no doubt that the true nature of 

 the composition of the pomegranate is to be explained upon 

 this principle. In order to make these considerations more 

 clear, let^s. 125, 126, and 127. represent — j^. 125. a convex 

 receptacle, with distinct carpels; Ji(/. 126. a concave one, with 

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



125 126 127 



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

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

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

 apparent. 



