202 
ORGANOGRAPHY. 
BOOK I. 
can be proved to exist between the latter and the stamens, 
unless it may be said to be indicated by those genera, such as 
Spiraea, in which the carpels are reduced to five ; and, finally, 
in such plants as Delphinium, in which the carpels are three, 
while the floral envelopes and male system are divided upon 
a quinary plan, it is manifest that no alternation can exist 
between the stamens and carpels. 
As the sepals and petals most commonly consist each of a 
single whorl of parts, so the pistil is more frequently composed 
of one whorl of carpels than of more. There are, however, 
certain families in which several whorls are produced one 
within the other, as in Fragaria, Ranunculus, Magnolia, 
Anona, and the like. In these cases it mostly happens that 
the carpels are either entirely separate or nearly so ; but it 
sometimes is found 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. 
125 126 127 
There oan be no doubt that the true nature of the com- 
position of the pomegranate is to be explained upon this 
