288 Beer, Development of the pollen grain and antlier of some Onagraceae. 
which was quite similar to that found in the walls of tlie pollen 
grains themselves. The air-passage in these anthers was there- 
fore oompietely shut off by a continuous mantle of thick, cuti- 
nisecl membranes. The thickening and cnticnlarisation of these 
walls had taken place very early in the history of the anther 
long before the pollen-walls themselves had nndergone such 
changes and indeed before tlie pollen-wall had put in its appe- 
arance at all (Fig. 1). 
Stomata occur npon the anther but they are not very 
abundant. In anthers at about the time when the pollen-mother- 
cells are established the development of the stomata can be 
readily followed. It is seen that an initial cell is cut off from 
certain of the meristematic superficial cells of the anther and 
this becomes the direct mother-cell of tlie stoma (Figs. 2, 3 
and 4). Starch can nearly always be found in the guard cells 
of the stoma altliough the other epidermal cells are quite free 
front this substance 1 ). 
I have examined the anthers of Gaura Lindlieimeri soon 
after tlie primary sporogenous cells have become definitely esta¬ 
blished by me ans of the cell-wall reagents recommended by 
Mangin. 
I find that both pectic bodies and cellulose are present in the 
walls of the anther-cells at this time but tliat the cellulose is 
ordinarily niasked by tlie pectic constituent. _ It is only after 
treating the sections with dilute acid followed by the action 
of dilute lalkali tliat the cellulose can be clearly demonstrated. 
The walls of the sporogenous cells and of the tapetuni contain 
less cellulose than the other regions of the anther. 
The walls of tlie primary sporogenous cells are at first no 
thicker than those of tlie surrounding tissues but they soon in- 
crease in thickness and stand out conspicuously from the neigli- 
bouring membranes. The very young 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 which 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 beeil grown and 
the time of day when tlie anthers have been fixed exercise, at 
all stages of development, considerable influence over the starcli- 
contents of the anther. 
Certain broad facts of starch-distribution, liowever, remain 
fairly constant in healthy plants grown under average con¬ 
ditions. 
In Gaura the single longitudinal series of primary sporo¬ 
genous cells becomes, without any further longitudinal division. 
the single column of pollen-mother-cells, eacli of which becomes 
i) A little starch occasionally occurs in the epi dermal cells of the cou- 
nective jnst over the vascular bündle, but never in any other part of the 
epidermis. 
