1918] DUDGEON—RUMEX CRISPUS 399 
the microspore mother cells are entering reduction (fig. 58). The 
cytoplasm becomes vacuolate, the nucleus stains very deeply, and 
shortly the entire protoplast collapses. 
Before the microspore mother cell stage, the epidermis over 
most of the anther begins to enlarge and thicken, and the pro- 
toplasts to disorganize. This thickening extends to the cells of the 
connective, so that each loculus becomes inclosed by an impervious 
layer, except in the stomial region (fig. 10). Here a plate of the 
<y 
Fic. 10.—Portion of transverse section of fully differentiated anther, showing 
thickened epidermis continuous with thickened connective, and permanently juvenile 
tissue (shaded), subsequent disorganization of which first connects the two adjacent 
loculi, then dehisces the resulting pollen chamber; 730. 
epidermis a few cells wide, together with the outer half of the tissue 
between adjacent loculi, remains undifferentiated, as a special 
mechanism for dehiscence. As the anther matures, these weak cells 
break down, first joining the cavities of the adjoining loculi to 
form the pollen chamber, then opening this chamber to the exterior. 
MICROSPOROGENESIS.—The- primary sporogenous cells under- 
go three or four successive divisions to form the completed sporoge- 
nous tissue. At the same time the anther has elongated greatly, 
