1 64 
MORPHOLOGY 
rogenous cell (fig. 388). The three uppermost segments and the cap 
develop the wall of the capsule, which is only one layer of cells thick. 
At the junction of the cap cell with the last segment is developed the 
stomium, which is a group of cells so arranged as to permit a cleavage in 
the wall of the capsule when it begins to dehisce. The annulus is a 
FlG. 386. Leaflet of Marattia, showing dichotomous venation and synangia 
(instead of sori). 
band of thick- walled cells which extends from the stomium over the 
top of the capsule and down on the other side to the stalk (figs. 385, 
39)- 
The primary sporogenous cell cuts off a sterile cell from each one of 
the four faces, these four cells developing the tapetum (figs. 388, 389). 
The centrally 
placed sporoge- 
nous cell then be- 
gins a series of 
divisions until 16 
mother cells are 
formed, which 
means a maximum 
output of 64 
387 
FIGS. 387-389. Sporangium of one of the Polypodiaceae : 
387, early stage, in which the outer papillate cell has begun to 
form the apical cell; 388 later stage, in which the cap cell and 
upper segments invest a central cell (primary spermatogenous), 
spores. Sometimes 
which has cut off one tapetal cell; 389. later stage, in which all there are only 8, 
the tapetal cells have been cut off and have begun to divide; the _ . _ pvpn 
central cell, by a series of divisions, forms 16 mother cells. 
mother cells. The 
tapetal cells break down, leaving the mother cells free in the enlarged 
cavity (fig. 390). 
These two kinds of sporangia, one from each extremity of the fern 
series, indicate not only a passage from the eusporangiate to the lepto- 
sporangiate habit, but also a striking reduction in the output of spores 
per sporangium. In this latter feature there is complete intergrading 
through the intermediate families. 
