346 BOTANICAL GAZETTE [May 
tive conditions will allow, and there are usually two methods by 
which this difficulty is overcome: by abortion of mother-cells, and by 
arrangement for a succession of sporangia according to nutritive 
supply. In Botrychium, however, there is no abortion of mother- 
cells and very little difference in the stages of development of the 
different sporangia in a spike. The nutritive supply is equal to the 
demand of all mother-cells, probably owing, in part, to the slow 
growth of the plant, and also to the large amount of food material 
stored in the stem. 
SUMMARY. 
1. The sporogenous tissue develops from a single hypodermal 
archesporial cell. 
2. As the successive sporogenous cells are formed, each retains 
its individuality throughout the development of the sporogenous tissue. 
3. Divisions in the sporogenous tissue are simultaneous up to 
the mother-cell stage. 
4. Beginning with the mother-cell stage, the sporogenous mass 
separates successively into blocks of cells in the same order in which 
the earlier cells were formed. : 
5. The blocks develop independently, and at a different rate in 
the same sporangium, though all cells of one block develop at the 
same rate. Whatever stimulus caused the simultaneity of division 
in early sporogenous tissue, is interfered with by separation of the 
cells into disjoined groups. 
6. The progressive separation of thc sporogenous mass is probably 
caused by the digestion of the middle lamellae. 
7- All mother-cells produce spores. 
8. The tapetum is of non-sporogenous origin. 
9. With the separation of mother-cell groups, the tapetum grows 
rapidly between them without the formation of walls; the nucle! 
increasing greatly in size, and dividing amitotically. 
10. The problem of nourishment in large sporangia may thus be 
solved by individual development of sporogenous cells, by their later 
separation into regular groups, and the rapid growth of tapetum 
between them. 
11. The nuclei of the old tapetum are four times the size of those 
in younger stages of its development. 
Pee ee 
