THE STAMEN 117 



the sections of the anthers in glycerine, and examine with a low 

 power. Note : 



1. The general outline of the section, and compare it with the 

 form of the bilobed anther as above observed. 



2. The two large cavities or pollen-sacs in each lobe. 



3. These are surrounded externally by the wall of the anther 

 \vhich consists of at least three layers of cells. 



4. The septa, which divide the two pollen-sacs or micro- 

 sporangia of each lobe from one another ; the anther has thus 

 originally four pollen-sacs : these may be found still distinct in 

 almost mature anthers, though as they approach maturity the 

 septa are partially broken down, and the cavities of the pollen- 

 sacs are thus thrown together : this usually happens before 

 the dehiscence of the anther. 



5. A single small vascular bundle * lying symmetrically 

 between the cavities in the central part or connective of the 

 anther. 



6. Pollen-grains or microspores, mostly to be found lying 

 free in the glycerine. 



Put on a high power and make the following observations : 



1. The wall of the anther is composed of 



(a.) A layer of epidermis, with an external cuticle : within 

 this is 



(.) A layer of cells with a fibrous thickening of the cell 

 walls. 



(c.) Immediately within (b) will be seen a narrow highly 

 refractive band, consisting of the remnants of two transitory 

 layers of cells, the inner of which was the tapetum : this is 

 almost completely disorganized ; the outer of the two layers, 

 which abuts on the fibrous layer, is less completely disorganized, 

 and may be seen as an almost continuous layer of thin-walled 

 cells, even in almost mature anthers. Note also that the wall 

 of the anther is thinnest, and its construction most simple at 

 the part most remote from the connective, i.e. where the septum 

 of each lobe meets the wall of the anther, while nearer to the 

 connective it becomes thicker. 



2. At the point where the septum meets the wall of the anther 

 the cells are smaller, and of rounded form, owing to the presence 



