FORMS AND UNION OF STAMENS 



127 



153. Form of the stamen ; union of stamens. Stamens are 

 of many specialized forms, to adapt them to their functions in 

 flowers of various shapes, but many are of the shape shown in 

 Fig. 129. Such a stamen consists of an ex- 

 panded part, the anther, borne on a stalk 

 called the filament. Anthers are often nearly 

 or quite sessile (seated, i.e. destitute of fila- 

 ments). Inside the anther is the powdery or 

 pasty substance called pollen (Fig. 153). 



Stamens may be wholly unconnected with 

 each other, or distinct, as shown in Figs. 122, 

 124, and 128, or they may be really or ap- 

 parently more or less united to each other. 



fl 



FIG. 129. Parts of 

 a stamen 



B, 



c, 



ive ; /, filament. 

 After Strasburger 



In Fig. 130 the stamens 



have arisen separately, 



but finally become joined 



together by their anthers 



(as is always the case in 



the family Composite). 



In other cases the stamens appear united 



when they are not really so, because they 



are borne on a ring or tube of tissue, as 



already explained in connection with the 



perianth (Sec. 152). 



Without regard to whether the union is 



real or apparent, stamens which occur in a 

 FIG. 130. Stamens of . , ,,, 1 . . ,. 



a thistle, with an- sm le g rou P ( the foments appearing joined) 

 thers united into a are said to be monadelphous (Fig. 131), in 

 rin two groups, diadelphous (Fig. 132), in many 



a, united anthers; /, g r0 ups, polyadelphous (the terms meaning 



filaments, bearded f 



on the sides. After one brotherhood, two brotherhoods, many 



Baiiion brotherhoods). 



154. The carpel. The simplest form of the organ which bears 

 the structures called ovules, that are to mature into seeds, is 

 known as the carpel. 



