A T otes. 
io 5 
but from the study and comparison of organisms which are believed 
to be nearer to the border line between Bryophyta and Vascular 
plants, viz. the Homosporous Pteridophyta . 
F. O. BOWER, Glasgow. 
PRELIMINARY STATEMENT ON THE SORUS OP 
DANAEA 1 . The sorus of Danaea, though its structure in the 
mature state has been repeatedly described, has not yet been studied 
as regards its development. 
The oblong, cake-like sori lie parallel to one another on the lower 
surface of the leaf, their longer axes following the course of the 
vascular bundles. Each sorus consists of two rows of loculi, of 
approximately equal size, completely sunk in the rather massive tissue 
of the wall. Dehiscence is described as being by a pore at the apex 
of each loculus. 
The sporogenous tissue of each loculus is usually referable to the 
segmentation of a single superficial cell, which gives rise to it, and to 
the portion of the sporangial wall above it. There is, however, great 
variety of bulk, number of cells, and mode of segmentation in adjoin- 
ing sporangia ; though the sporangia of the same sorus develop 
simultaneously, such extreme differences of number as between four 
and sixteen cells may be seen in the same section. Moreover, the 
whole sporogenous group is not always referable to a single parent 
cell. These facts stand in marked contrast to the uniformity of size 
and segmentation so characteristic of the Leptosporangiate Ferns. 
The dehiscence is by slits, which appear in the sporangial wall 
above the loculus. By the drying and contraction of the adjoining 
cells the slit gapes widely, and appears as a pore ; but the details are 
very like those of other Marattiaceae, excepting that there is no 
‘ annulus ’ of indurated cells. This, which is absent in Danaea , 
where the loculi are deeply sunk, is present in those Marattiaceae 
in which the sporangia project as separate papillae. In the latter 
case the annulus is mechanically effective in widening the slit ; in the 
former, the sporangia being closely united, such mechanical effect 
would be impossible. 
Though the loculi of a sorus are frequently of nearly uniform size, 
1 Read before the Royal Society, Dec, 5, 1895 : reprinted by permission from 
Proc. Roy. Soc., No. 354, Vol. lix. 
