*JSS Beer, Development of the pollen ^rain and antlier of some Ona^raceae. 



whicli was (juitc similar to tliat found in the walls of the pollen 

 grains themselves. The air-passage in these anthers was there- 

 fore completely shut off by a continuous mantle of thick, cuti- 

 nisod menibraiU'S. The thickenin<i; and cuticnlai-isation of these 

 walls had taken ])hu'c verv carly in the history of the antlier 

 lonn; before the pollen-walls thcmselves had undergone such 

 ehanges and indeed before the pollen-wall had put in its appe- 

 arance at all (Fig. 1). 



Stomata occur upon the antlier but they are not veiy 

 abundant. In anthers at about the tinie when the pollen-mother- 

 cells are est'ablished the development of the stomata can be 

 readily followed. It is seen that an initial cell is cut off from 

 certain of the meristematic sujierficial cells of the anther and 

 this becomes the direct mother-cell of the stoma (Figs. 2, 3 

 and 4). Starch can nearly always be found in the guard cells 

 of the Stoma although the other epidermal cells are quite free 

 from this substance^). 



I have examined tlie anthers of Gaura LindJieimeri soon 

 after the primarv sporogenous cells have become definitely esta- 

 blished by means of tlie cell-wall reagents recommended by 

 Mangin. 



I find that botli pectic bodies and cellulose are present in the 

 walls of the anther-cells at this time but that the cellulose is 

 ordinarily masked by the pectic constituent. It is only after 

 treating the sections witli dilute acid followed by the action 

 of dilute alkali that the cellulose can be clearly demonstrated. 

 The walls of the sporogenous cells and of the tapetum contain 

 less cellulose than the other regions of the anther. 



The walls of the primary sporogenous cells are at first no 

 thicker than those of the surrounding tissues but they soon in- 

 crease in thickness and stand out conspicuously from the neigh- 

 bouring membranes. The very j^oung anther contains only a 

 trace of starch in fine granules. The occurrence of starch can 

 first be detected in the filament of the stamen, it then spreads 

 upwards to the cells of the connective wliich lie dorsal to the 

 vascular bündle and it can next be seen in the primary sporo- 

 genous cells. This is the usual sequence of starch appearance 

 but the conditions under which the plant has been grown and 

 th.e time of day when the anthers have been üxed exercise, at 

 all stages of development, considerable influence over the starch- 

 contents of the antlier. 



Certain broad facts of starch- distribution, however, remain 

 fairly constant in liealthy plants grown under average con- 

 ditions. 



In Gaura the single longitudinal series oi primary sporo- 

 genous cells becomes, without any further longitudinal division, 

 the Single column of pollen-mother-cells, each of which becomes 



1) A little starch occasionalty occurs in the epidermal cells of the con- 

 nective just over the vascular bündle, but uever in any other part of the 

 epidermis. 



