288 BOTANICAL GAZETTE [ocroner 
organizing sporogenous cells, and a secretion poured out by the 
tapetum, which is the source of nourishment of the two young 
spores. 
The spore membrane itself is a somewhat viscid substance, almost 
fluid in character, that flows out of the hole if a living sporangium 
be pricked with a needle. The spore membrane becomes much 
thicker at the base of the spore, so that the remarkably small pro- 
toplast lies near the apex (jig. 5). The growth and differentiation 
of the spore membrane into regions are extraordinarily rapid. Just 
inside of the clear area described above, a part of the membrane is 
much denser than elsewhere. These two regions, 7. e., the clear and 
the denser (fig. 5), constitute the preliminary stage of the first or 
outside coat, the exospore. It is possible in a close series of prepara: 
tions to note gradual changes in structure as the coat matures. 
Chemical tests to determine the nature of the transforming spore 
membrane and of the resultant coats were very unsatisfactory. In 
all early stages the minute living spores are so difficult to manipulate 
that no reliable results could be obtained. On the other hand, 
material that is sectioned and upon the slide where it can be handled 
has already been subjected to the action of many reagents. The 
clear area, or outer layer of the exospore (fig. 6), is gradually trans- 
formed into a granulated condition, while the inner layer and the 
rest of the spore membrane becomes reticulated. All the regions 
are quite distinct and react differently to the stains used. 
Up to this time the protoplast has not altered in size oF 
but now it suddenly dilates—like a bubble which is blown up ; 
presses outward toward the exospore. When its diameter a“ 
half that of the entire spore, a second delicate coat, the endospor’ 
may be detected, having formed upon the outer surface of the oe 
toplast. This is difficult to demonstrate unless the coat gp : 
plast become torn apart and displaced; for it is little more aap 
faint line in section during the entire period that the protoplast 
expanding and pressing it back against the outer coat. pele ato 
of the spore membrane (fig. 6) which is not directly transfo ), dis 
the exospore, and against which the protoplast presses (78: ee 
appears as the protoplast and endospore dilate. As the € ; 
has been undergoing modifications (figs. 7 and 8, ¢é) — 
density, 
