200 PRACTICAL BOTANY 



THE STAMEN. 



III. All the following preparations should be made 

 from materials hardened in alcohol, or fixed with 

 saturated solution of picric acid, and then washed, and 

 hardened in alcohol. 



A. Cut transverse sections of a flower bud of Caltha 

 palustris, which was just ready to open, taking care 

 that the anthers shall be cut through transversely. 

 Neglecting the other parts, mount 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, which consists of at least three layers of cells. 



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

 microsporangia 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 de- 

 hiscence of the anther. 



5. A single small vascular bundle lying symmetri- 

 cally between the cavities in the central part or con- 

 nective of the anther. 



6. Pollen-grains or microspores, mostly to be 

 found lying free in the glycerine. 



