in Blechnum and Osmunda. 
35 
cell-wall and escape of the secretion the ectoplasm and the 
disorganised nucleus are the only structures which still remain 
in connection with the cell-membrane, the dead and equally 
disorganised endoplasmic framework escaping with the 
mucilage (Figs. 9 and 27). 
Tannin can be demonstrated in quite young cells, and from 
this point onwards it steadily increases in amount, although it 
never occurs in such great quantity as in Osmunda. With the 
exception of its transverse basal wall the cell-membrane 
undergoes cuticularisation over the whole of its surface, but it 
is only the more external of the wall-lamellae that are thus 
affected. The inner layers retain for some time their primitive 
cellulose character, but at length they suffer hydration and 
become converted into a substance of a mucilaginous nature. 
This latter, although it undergoes but little swelling, is capable 
of great extension, as the very large size of the bladder-like 
glands sufficiently proves. The transverse basal wall, which 
separates the head from the contiguous stalk-cell, is much 
more pronouncedly mucilaginous, and gives a well-marked 
pink colour with corallin-soda. 
We are now in a position to describe in detail the various 
phenomena connected with mucilaginous secretion. We have 
already stated that this substance is directly derived from the 
protoplasm, and we may further add, that the various changes 
which give rise to its formation are undoubtedly of a katabolic 
nature. In all the cases which we have investigated the 
mucilage arises in the form of small drops, all of which grow 
to a fixed definite size, and the number of the drops is con- 
tinually increased by repeated basipetal formations until the 
energy of the protoplasm is exhausted and the gland-cell is 
full (Figs. 1 6 and 17). The first few drops appear to burst 
into the vacuole, causing it to assume a certain mucilaginous 
character, but, apart from this exceptional phenomenon, all 
the various drops remain distinct, each being completely 
shut off from its neighbour by its own portion of the delicate 
protoplasmic reticulum which constitutes a framework for the 
whole system of drops in the secretory cell. 
