342 BOTANICAL GAZETTE [MAY 
the blocks is apparently thicker, and by the time the spirem is 
formed the blocks have begun to separate. This separation takes 
place in the order in which the original walls were laid down in the 
archesporium and young sporogenous mass (jigs. 3, 4, 6, 7). At 
about prophase the mass has separated into at least sixteen (in section) 
distinct and separated masses (fig. 6). ‘‘About” prophase is used, 
since with the separation of the blocks differences in stages of division 
begin to appear, so that the cells throughout the entire sporogenous 
mass are not in the same stage, though those in the same block are 
always in the same stage. 
The progressive separation into smaller blocks continues in the 
same manner in which the first blocks were formed. It takes place 
along the same lines and in the same order in which the earlier walls 
were laid down. Whatever stimulus caused the simultaneity of divis- 
ion during the early life of the sporangium seems to have been 
interfered with here by the cleavage into disjoined blocks, 
for in the same sporangium the blocks are in different stages of 
division, it being quite common to find four or five stages. For 
example, in three adjacent blocks, the cells of one were in early meta- 
phase, of another in telophase, and of the third in anaphase. In 
another case blocks were found in the same sporangium varying from 
metaphase of first to metaphase of second division; and it is very 
common to find them varying from metaphase of first to prophase of 
second division. One sporangium was found in which all the cells 
of one-half the entire sporogenous mass were in metaphase, while 
those of the other half were in telophase. All of the sporogenous 
tissue throughout its entire development appears in a vigorous and 
perfectly normal condition. 
What may be the cause of this retention of their individuality by 
the developing sporogenous cells is difficult to say. In regard to bryo- 
phytic antheridia this phenomenon has been explained as due to the 
independent development of the original spermatogenous cells; and 
there is no further blocking of the spermatogenous mass after the 
periclinal walls which cut off this mass from the antheridial wall 
layer have been formed. The difference in rate of development of 
these blocks has been attributed to differences in food supply, oF '° 
some purely physiological cause. It seems that as much might be 
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