XV THE DEVELOPMENT OF THE FLOWER 197 



modified for special work that of producing pollen. The fila- 

 ment represents the petiole of the foliage-leaf, and it is traversed 

 by one or more . vascular bundles, which is surrounded with 

 endodermis. The vascular cylinder is surrounded by paren- 

 chyma cells, and these again by an epidermis. As a rule there 

 are no stomata in the epidermis of the filament. 



The anther represents the blade of the foliage leaf folded to 

 form four cavities \hzpollen sacs. Up the centre of the anther, 

 and dividing it into two lobes is a midrib the connective. In 

 the centre of the connective runs a vascular bundle, continuous 

 with the bundles of the filament, and bringing nutritive matter 

 to the anther. The walls 

 of the mature anther, as 

 seen in a transverse sec- 

 tion, consist of the follow- 

 ing parts ; 



I. The epidermis, the 

 outer walls of which have 

 a well-developed cuticle, 

 and may contain a few 

 stomata. 



T7, -fih~* /,,, FIG. 205. Transverse section of anther of Wall- 



2. The fibrous layer flower ;> ^ wall of pollen sacs . vbt vascu i ar 

 consisting of several bundle, 

 layers of cells, which 



present a stratified appearance, due to the thickening of the 

 walls. 



3. The tape turn layer, sometimes represented by nearly dis- 

 organised cells, for it is used for the nutrition of the pollen 

 grains. The young anther contains four pollen sacs, but the 

 mature one only two ; this is owing to the two pollen sacs in 

 each lobe of the anther uniting just before it becomes ripe. 

 The pollen sacs contain pollen. Each pollen grain is a male 

 reproductive cell. 



The Development of the Stamens. The first part of 

 the stamen to appear is the anther, and this is formed by the 

 division of a number of cells just below the epidermis. These 

 cells -are, because of their position, called hypodermal cells ; they 

 form what is called the archesporium or meristem layer from 

 which the anther and pollen grains are formed. The cells of the 

 archesporium divide at four points in the young anther, which 



