es FILICALES 
marked a feature in Ferns at large that these irregularities command the 
greater attention. Fig. 286 a represents a tangential section traversing 
three sori in Danaea elliptica, of an age prior to the tetrad-division: the 
varying size of the sporangia is striking, as also their frequent grouping 
in pairs, separated by a thin, or even by a partial septum. Some of 
Danaea elliptica, Smith. Drawings illustrating partial septations of the sporangium. 
A, tangential section through three sori, showing the loculi in ground plan: the septa are 
often thin, so that pairs of loculi are in close juxtaposition; the loculi marked (x) 
are large, and show one or more partial septa. 20. B,C, D, #, show such loculi with 
partial septa in greater detail: in D and £ it is difficult to decide whether the cells 
marked (?) will develop as tapetum or as spore-mother-cells. 150. 
these partially septate sporangia are represented more in detail in 
Figs. 286 p-E. From these drawings it is clear that the identity of the 
sporangium is not maintained: that where the initial sporogenous group 
is large, some of its cells may develop as transitory tapetum, or even as 
permanent cells of septal tissue: and thus various intermediate steps of 
completion of a septum may be observed. Somewhat similar conditions 
