in Blechnum and Osmunda. 51 
other hand have to work their way bodily through the proto- 
plasmic membrane in order to escape to the exterior. This 
is probably brought about by a series of actual minute 
rupturings of the substance of the protoplasm, which no 
doubt at once heal, and the final escape to the ex- 
terior is possibly attended by the production of inflated 
bubbly protrusions, which burst in a manner essentially 
similar to that which occurs in the young cells of Osmunda 
and Blechnum in the case of certain of the first formed 
mucilage-drops. The passage through the cell-wall is a 
comparatively easy matter. Whether or not the cuticle is 
raised depends upon the density of the secretion and the 
degree of cuticularisation. Should the secretion, instead of 
escaping to the exterior, pass into the vacuole the pheno- 
mena are quite similar in detail, except that the inner mem- 
brane (hautschicht) of the endoplasm instead of the external 
membrane of the ectoplasm would have to be taken into 
account. 
Botanical Laboratory, Cambridge, 
May 26, 1887. 
EXPLANATION OF FIGURES IN PLATES III & IV. 
Figures 1-32 illustrate Blechnum occidentals , except Fig. 4 ( Ceratopteris 
thalictroides ) and Fig. 7 (. Blechnum brasiliense). Figs. 33-44 illustrate Osmunda 
regalis. 
(Where not otherwise stated the drawings are taken from fresh specimens.) 
Fig. 1. One of the paleae from the young shoot bearing numerous mucilage- glands. 
Fig. 2. A similar palea bearing resin-glands. 
Fig. 3. Apical portion of a very young bud, showing the young mucilage and 
resin-cells developed from the epidermal cells. 
Fig. 4. Early stages in the development of Ceratopteris thalictroides (after 
Ivny). The terminal cell which will become the mucilage-gland is already well 
developed. 
