STAMENS. 



91 



(fig. 214 ^). There are forms allied to this last-named plant in which the anthers 

 show very complicated convolutions— like those of the human brain. 



When the time draws near for the pollen to leave its place of origin, its cells 

 — whether in a loose powder or sticking one to another — become free from the 

 inclosing wall of the anther, and lie embedded in the cavity of the pollen-sac, 

 as it were in a purse or pocket, awaiting their release. The pollen-sac, hitherto 



rig. 216.— stamens. 



L Calavdrinia compressa. 2 Sola/ivwm Lycopersicum. s Galanthus nivalis. * Cyclamen eurepceum. 6 Rammidia pyrenaica. 

 6, 7 Cassia Unitiva. 8 Pyrola rotwncLifolia. ^ Arctostapkylos Uva-ursi. lo Arctostaphplos alpina. n Vaccinium 

 uliginosum. 12 Pyrola unijlora. is Medinilla (after Baillon). 1* Vacciniwm oxycoccvs. is Calceolaria Pavonii. 

 16 Tozda alpina. i», i' SiVbaldia procumbem. is Oaleopsis angwstifolia. '^, 21 Mrythrcea Centaureum. 22_ ss Melissa 

 officinalis. 24_ 25 Calla palustris. 26 Nyctandra (after Baillon). 27^- 28 Globularia eordifolia. 23_ so Theohrama Cacao. 

 81 Pinguicula vulgaris. *2 Qarcinia. (All somewhat enlarged.) 



closed, now opens, and the pollen is liberated. This opening or dehiscence of the 

 pollen-sacs is accomplished in various ways. It has been already explained that 

 most young anthers contain four sacs which rarely all remain distinct, but, by 

 the breaking down of the parti-walls between each pair, become merged into 

 two cavities. 



These two cavities may be spoken of as anther-halves. In cases where the 



