1905] CARDIFF—SPORANGIUM IN BOTRYCHIUM 343 
said of the blocking in a Botrychium sporangium; though each divis- 
ion, from the very first almost to the formation of the mother-cell, 
separates masses which retain their individuality throughout their 
further development. The rate of growth, however, and apparently 
the food fupply are absolutely the same for all the blocks up to the 
mother-cell stage. It would seem that in such large sporangia some 
blocks or cells would be more favorably located than others with 
reference to food supply or conditions of growth, and there would 
be greater growth on the part of some regions than others, thus 
causing irregularities in the arrangement of cells, such as is found in 
most sporangia, instead of the very regular arrangement in those of 
Botrychium. Therefore, the above mentioned physiological explana- 
tion in regard to bryophytic antheridia is not entirely satisfactory. 
What may be the exact cause of this progressive separation of the 
sporogenous mass along lines where the earlier walls were laid down 
is impossible at present to say. To me, the most reasonable explana- 
tion which can be offered is that the middle lamellae of the walls are 
acted upon by an enzyme at a time when the sporogenous mass is 
greatly in need of food. As the lamellae grow older their composi- 
tion may change, so that they are more easily digested than those 
more recently formed, thus effecting a progressive separation of the 
sporogenous tissue. As the blocks become separated, and wholly 
or partially surrounded by the tapetum, some blocks will of necessity 
be under slightly different conditions of osmotic pressure or chemical 
stimulation than others, thus bringing about differences in the rate 
of their development. 
In Botrychium the tapetum is derived from the wall, and absolutely 
no contribution is made to it from the sporogenous tissue. By the 
time the sporogenous mass has reached as much as sixty-four cells, 
the tapetum is clearly delimited from the sporangial wall and is two 
cells in thickness. From this time on periclinal divisions take place 
rapidly until the spore mother-cell stage is reached, when the tapetum 
is four or five cells in thickness and very glandular in appearance. 
At the first separation of the blocks (figs. 3 and 4) in the sporogenous 
mass—about the synapsis stage—the cell walls of the inner layer of 
tapetal cells begin to disintegrate. Some of these inner cells are at 
this time binucleate, while the nuclei of the next one or two layers 
