252 BOTANICAL GAZETTE [APRIL 
how the bud is protected by its hairy covering. Most of these hairs 
have a double function. While young they act as slime cells in 
keeping the growing point and growing tissues moist, this function 
being best performed by the hairs on the tips of the sepals and bracts, 
and the bases of the carpels. These young hairs are long and tortu- 
ous, and wind among the growing rudiments (fig. 9). Their cavities 
are full of sap, and their nuclei take a very dark stain; they remain 
in this active stage longer than hairs on other parts of the plant. As 
they grow older all the hairs acquire thick cell walls, and tend to 
straighten. In their mature state they act as a protection against 
moisture. This function they perform by means of a waxy covering 
which repels water, so that it is very difficult to moisten a young 
flower bud, or a growing twig, or fruit; but if these hair-covered parts 
be soaked a short time in strong alcohol, and allowed to become dry 
again, they may be very readily moistened. 
POLLEN SACS AND POLLEN. 
Each fertile stamen rudiment begins early to form two microspo- 
rangia. There is apparently no evidence of the presence, at any stage; 
of the other two microsporangia that are usually found in angio- 
sperms. No indication of pollen-formation is ever seen in the sterile 
rudiments. 
The first evidence of the formation of the archesporium is found 
about the middle of June. The subepidermal layer divides by pet! 
clinal walls at the place where the microsporangia are to be formed 
(fig. 1). The exact derivation of layers is hard to trace, but it is quite 
certain that it is from the inner layer thus formed that all the arche- 
sporial tissue comes. By the middle of July the archesporium is well 
blocked out, and shortly after the spore mother-cells are formed. At 
this stage there is about them a moderately well-defined tapetu™ 
and the outside wall of the microsporangium is three or four ce 
layers in thickness (fig. 2). Here the pollen mother-cells are only 
noticeable by their slightly larger nuclei and more deeply staining 
contents. 
The further growth of the microsporangium is brought about by 
the increase in size of its cells, both sporogenous and tapetal. 
Before the tetrad division, the nuclei of the tapetum divide without 
