1 2 4 
The Ohio Naturalist. 
[Vol. VII, No. 6, 
this periclinal division is taken as the first cell of the sporangium, 
and its development will be traced as closely as possible. 
The division of this first cell is anticlinal and may occur either 
radially to the sporangiophore (Fig. 3) or in a plane perpendic¬ 
ular to the radius (Fig. 2). But no case was found where it 
occurred periclinally. The second division takes place either 
periclinally or anticlinally and in either case the divisions in the 
two daughter cells are the same so that we have two plates of 
two cells each side by side. Further development of the spo¬ 
rangium takes place in various ways. 
In general, however, the sporangia may be divided into two 
types which are correlated with the direction of this second 
division. It was noticed that when the wall was periclinal after 
a radial anticlinal division of the first cell, the sporangium 
formed was broad and rounded (Figs. 5, 14-18), while if the wall 
was anticlinal the sporangium was long and slender (Figs. 2-4, 
6-13, 19). 
The next division of the broad rounded type of sporangium, 
where the second wall is periclinal, is in the outer of the two pairs 
of cells which divide anticlinally (Fig. 5). These daughter cells 
may then divide either periclinally or anticlinally, the usual 
method, however, is for two or three walls to be formed anti¬ 
clinally after which these cells divide (Figs. 14-16). The devel¬ 
opment of the inner cell is retarded (Figs. 15, 16) until about the 
time the tapetum is differentiated when it becomes active 
(Figs. 17, 18). The progeny of the outer cell does not divide 
as rapidly from now on as that of the inner cell. About this 
stage there is a differentiation of wall and tapetum and a little 
later the cells between the wall and tapetum become flattened 
along with the tapetum as the sporogenous tissue develops. The 
sporogenous tissue seems to come from both the inner and 
outer cells (Fig. 18). 
The long slender type of sporangium, in which the second 
division is anticlinal, shows striking differences in development. 
The third division is periclinal and seems usually to be in the 
upper of the two pairs of cells (Fig. 6) both pairs, however, 
divide rather rapidly (Figs. 6-13) until in radial section there are 
two long rows of cells very separate and distinct from each other. 
When the number of cells in longitudinal section of the sporan¬ 
gium is about twelve or fourteen (Fig. 13) the tapetum begins to 
form and soon after, the cells of the sporogenous tissue begin to 
divide in the other direction also and a sporangium develops 
which compared with the other kind is rather long and slender 
(Fig. 19). This method of forming the sporangium does not 
seem to have been recorded by any who have worked on Equi- 
setum though Bower mentioned that in E. limosum the develop¬ 
ment was somewhat irregular.. 
