78 The Natural System of Botany. 



principal characters derived from the stamens depend upon 

 the manner of their insertion into the lower part of the flower. 

 In some cases they spring from beneath the ovary, in which 

 case they are said to be hypogynous, and are separately inserted, 

 with the petals and sepals, on the disk. Sometimes they 

 adhere for a part of their length to the calyx, their points of 

 insertion being the same with the sepals, which, when they 

 are detached, carry away the stamens with them; or they 

 adhere in a similar manner to the petals. In these cases the 

 stamens are perigynous. In other instances the stamens are 

 closely enveloped by the calyx, which also embraces the 

 ovary, so that they appear to arise from its upper part. Li 

 this case they are epigynous. Figure 1. represents sections of 

 flowers showing these modifications. In a the stamens are 

 hypogynous, in b, perigynous, and in c, epigynous. 



Figure 1. 



The manner in which the anthers open to disperse the pol- 

 len, is sometimes characteristic of an order. In the Barberry 

 tribe, for instance, they open into valves, like the pod of a pea, 

 or a little box, and in the Heath tribe they have pores through 

 which the pollen is projected. These peculiarities are not to 

 be implicitly relied on. Of all natural characters, those 

 afforded by the central parts of the flower are probably the 

 most invariable. The number of styles, like that of the sta- 

 mens, is subject to variation, though not in so great a degree, 

 and in some genera it is quite constant ; but the carpels, or 

 separate parts of the pistil, each of which contains a soea, 



