xxx Sl'OKOPHYLLS 381 



The third whorl is called collectively the andr&dum, and 

 consists of a variable number of stamens or male sporo- 

 phylls (.$/>.;>//. $, ). Each stamen is along narrow leaf bearing at 

 its distal end four microsporangia (pollen sacs, ;///. spg) united 

 into a lobed knob-like body, the anther. The microspores 

 (c 1 ) are at first simple cells with double cell-walls, but sub- 

 sequently the protoplasm becomes divided into two cells, 

 as in Gymnosperms, a smaller (a) and a larger (b\ The two 

 are not, however, separated by a firm septum of cellulose, 

 and the smaller cell frequently comes to lie freely in the 

 protoplasm of the larger. Moreover it appears that the 

 nucleus of the smaller is the active agent in fertilization, and 

 that the larger must therefore be considered as representing 

 the vestigial prothallus. 



The fourth or distal whorl of the flower is called collec- 

 tively the gywzcium or pistil, and consists of one or more 

 carpels or female sporophylls (sp. ph. 9), which are modified 

 in a characteristic manner. In some cases each carpel (B 1 , 

 B 2 ) becomes folded longitudinally along its midrib (m.r), and 

 its two edges, thus brought into contact, unite so as to 

 inclose a cavity. Concrescence only affects the proximal 

 part of the carpel, which thus becomes a hollow capsule, the 

 venter (so-called ovary, A, v) : its distal portion usually takes 

 the form of a slender rod-like body, the style (st), terminated 

 by an enlarged extremity, the stigma (stg) which is covered 

 with hairs and is frequently sticky. In some flowers, on the 

 other hand, all the carpels of the gynsecium unite with one 

 another by their adjacent edges, so as to inclose a cavity 

 common to all : in this case also the hollow portion or venter 

 is formed by the proximal part only of the carpels, their 

 distal portions forming a simple or multiple style and 

 stigma. 



The megasporangia (ovules, A and B, mg. spg) are usually 



