136 ELEMENTS OF STRUCTURAL BOTANY. 



The cells of anthers commonly open along their outer 

 edges to discharge their pollen (Fig. 185). In most of the 

 Heaths, however, the pollen is discharged through a 

 minute aperture at the top of each cell (Fig. 186), and in 

 our Blue Cohosh each cell is provided with a lid or valve 

 near the top, which opens on a kind of hinge (Fig. 187). 

 Occasionally, examples of barren or abortive stamens are 

 met with, as the fifth stamen in Turtle Head and 

 Pentstemon. These are filaments without anthers, and are 

 known as staminodes. 



212 Stamens may be either entirely distinct from each 

 other in which cise they are described as diandrous, 

 pentandrous, octandrous, &c., according to their number 

 (or, if more than twenty, as indefinite) or 

 they may be united in various ways. If 

 their anthers are united in a circle, while 

 the filaments are separate (Fig. 57), they 

 are said to be syngenesious ; but if the 

 filaments unite to form a tube, while the 

 Figs. 185. 187. 186. anthers remain distinct, they are said to be 

 monadclphous (Fig. 32) ; if they are in two groups they 

 are diadelphous (Fig. 37) ; if in three, triadelphous ; if in 

 more than three, polyadelphous. 



213. As to insertion, when stamens are inserted on 

 the receptacle they are Tiypogynous ; when borne on the 

 calyx, perigynous ; when borne on the ovary, epigynous ; 

 and if inserted on the corolla, epipetalous. They may, 

 however, be borne even on the style, as in Orchis, and 

 then they are described as gynandrous. 



214 If the stamens are four in number, and in two 



Figs. 185, 186, 187. Anthers exhibiting different modes of dehiscence. 



