in Blechnum and Osmunda . 
45 
does arise from the inner layers of the cell-membrane, but 
de Bary 1 with his customary caution merely remarks that 
‘ the origin of this mucilage has yet to be investigated.’ 
As a matter of fact the development is precisely similar to 
that which we have described in Blechnum. Here also 
the secretion arises in the form of isolated drops, which at 
first bud into the cell-cavity, and are subsequently increased 
basipetally until the cell is full (Fig. 40). In Osmunda the 
drops are both smaller and more numerous. In each drop 
a further differentiation into droplets takes place, but the 
comparative difference of density of the two structures is 
not nearly so great and as a consequence the droplets are 
somewhat difficult to define, but by appropriate swelling 
in water and staining in methylene-blue the whole structure 
may be clearly seen. In the denser peripheral mucilage 
even the drops themselves are difficult to distinguish without 
preparation, and the protoplasmic framework is slight and 
fine. Neither chromic nor osmic acid can be employed 
for the examination of the fresh hairs on account of the 
enormous quantity of tannin, which stains the whole structure 
so deeply as to render satisfactory observation quite im- 
possible. Iodine gives striking and beautiful results, and, 
as our figure (Fig. 40) shows, one may bring out in the 
mature cell the nucleus, the drops, and the framework with 
great distinctness and effect. See also Fig. 41, where the 
drops are seen from the outside. The secretion of the drops 
commences in very young cells, and some of the drops first 
formed appear to burst into the cell-vacuole as in Blechnum. 
For a long time the starch, which is present in the cell in 
great quantity, takes no active part in the drop formation, 
but, as the zone of secretion spreads, they gradually break 
down and disappear. The degeneration, both of the starch 
grains and of the nucleus, is usually accompanied by the 
frothy and utriculated appearance which characterises such 
degenerations as that of the chlorophyll-corpuscles of Chara 
1 De Bary, loc. cit. 
