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 receptacle 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 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 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 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- 
125 126 127 
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. 
