36 Gardiner and I to. — On Mucilage-cells 
The successful observation of the developing drops was 
found to be one of the most difficult points connected with the 
present research, but by the use of osmic acid we were at 
length able to set the matter at rest, and subsequently also 
to observe the same phenomenon in fresh glands. As our 
figure (Fig. 1 6) shows, the development commences at a very 
early period. Our drawing was taken from a hair which had 
been treated with a i per cent, solution of osmic acid. The 
mucilaginous contents of the vacuole are contracted by the 
action of the reagent, leaving a portion of the lining proto- 
plasmic membrane and of the threads going to the nucleus 
clear and free. At various points here and there numerous 
small bubble-like utricles may be seen, and these represent 
the young developing mucilage-drops. The secretion arises, 
as we have already stated, just below the surface of the endo- 
plasm, and the drop, enclosed by its delicate protoplasmic 
membrane, protrudes into the cell cavity. Having reached a 
definite size, its growth ceases and a new drop soon com- 
mences to form just below, and thus by repeated basipetal 
formations immediately beneath the various drops contained 
in the cell, the latter becomes after a time quite filled by them 
and even the vacuole-space is entirely eliminated. Fig. 17 
shows in a very clear manner the formation which we have 
described. In the adult cell the protoplasm appears as a 
delicate reticulum containing the various drops in its meshes, 
the whole system being bounded by the ectoplasm and con- 
tained within the cell-membrane (Figs. 11 and 19). All the 
protoplasm is for some time living and functional, but in course 
of time it experiences degeneration-changes, and ultimately 
death ensues, commencing in the more central protoplasm and 
gradually spreading to that at the periphery. The remains 
of the disorganised framework may be brought into view by 
staining the cell with iodine when it appears as a number of 
deeply-staining granules which still mark out the boundaries 
of the separate mucilage-drops (Fig. 19). In the fresh and 
fully-developed cells, especially of the leaves (Fig. 20), it is often 
indistinguishable, but may be readily demonstrated by the use 
