THE WALLFLOWER 111 



line, and at the same time the partition separating the 

 sacs is broken down (see Eig. 40, w), so that a single 

 opening serves for the escape of the pollen from each 

 pair of pollen-sacs. At the time of dehiscence, there- 

 fore, the anther appears to have only two cavities, and 

 we have to go back to unopened anthers to find the 

 four pollen-sacs intact. 



We see, then, that the stamen is a modified leaf, 



FIG. 40. Transverse section of ripe anther of Wallflower, 

 after dehiscence. Observe that the two pollen-sacs on 

 each side have now opened into each other by the break- 

 ing down of the wall w between them, v.b, vascular 

 bundle of connective ; p.s, the four original pollen-sacs ; 

 /, fibrous layer. Magnified 44. (R. S.) 



bearing four pollen-sacs, which produce in their interior 

 numerous pollen-grains. It will now be well to trace 

 the development of the pollen-sacs, and of the pollen 

 which they contain. 



The anther is the first part of the stamen to be 

 developed, so that in a moderately young stamen we 

 find the anther almost full-grown while the filament 



