44 Gardiner and I to. — On Mucilage-cells 
hair is composed, and the escape of the mucilaginous contents 
is then a very easy matter (Fig. 44). In certain instances, 
however, the rupture and escape takes place as in Blechnum . 
The mucilage of the mature glands when examined in 
water appears dense and horny. As in Blechnum hrasiliense 
there is a marked distinction between the looser and more 
granular central core (Fig. 40) and the highly refractive 
and lamellated peripheral portion of which the bulk of the 
secretion consists. On the addition of alcohol the layering 
becomes much more evident, and at least three well-defined 
zones may then be distinguished (Fig. 43) ; the peripheral 
portion, already referred to, undergoing further differentiation 
into two or more concentric strata. This separation into 
layers evidently depends upon the constitution and tension 
of the various parts of the mucilaginous secretion. The 
centremost portion represents the first formed mucilage as 
in Blechnum brasiliense. The most external and densest 
layer is, on the contrary, of the more recent formation. It 
is exposed to some pressure and it differs also in constitution, 
since, as we shall see further on, starch largely enters into 
the composition of it. The middle zone consists of mucilage 
practically free from starch, being derived purely from the 
inner portions of the endoplasm ; and here the pressure is the 
greatest of all, since it is situated between the central core 
which, being most disorganised, swells to the maximum and 
refuses to yield, and is also exposed to the pressure of the 
outer zone in which new drops are continually being formed 
and pushed towards the centre. See also Fig. 40, which 
shows relative pressure of drops. 
We may now describe the mode of secretion. If in 
Blechnum brasiliense it appears that the mucilage is partly 
derived from the cell-wall, so much the more is this the 
case in Osmunda , where even the layering which accompanies 
ordinary mucilaginous degeneration is wonderfully simulated 
(Fig. 44). Goebeler *, indeed, actually states that the mucilage 
1 Goebeler, loc. cit. 
