of Water in Mosses . 15 1 
tinctly visible, brown colouring matter of cell-walls of hypo- 
dermal sterome dissolved ; section removed to cold solution 
(concentrated) of caustic potash , the distorted cuticle still 
more obvious than before. Middle lamellae of sterome 
dissolved. Cell-walls of sterome and epidermis do not swell 
even on being heated in nitric acid and chlorate of potash ; 
swelling takes place immediately on removal to caustic potash. 
If, after boiling for some time in mixture — the colour being 
completely lost — section is then treated with iodized zinc- 
chloride, cell -walls give characteristic cellulose -blue. If 
action is not prolonged, the cuticle, coloured yellow by the 
iodized zinc-chloride, may be well seen. 
Sections through the apophysis and sporangium give 
similar results to those detailed above for the seta. The 
guard-cells of the stomata are seen to be covered by a 
delicate cuticle when treated with iodized zinc-chloride ; but 
the rest of the thick wall of the guard-cell becomes blue 
and in the innermost parts of the wall almost colourless, 
in this way forming a strong contrast to the other epidermal 
cells, all of which are deep yellow. 
It is obvious from the reactions given above that the 
epidermis of the seta, apophysis, and sporangium is strongly 
cuticularized, and that there is on the outside of the epidermis 
a distinct cuticle. The hypodermal sterome appears from 
the reactions to contain both lignin and cutin (cf. effect 
of chromic acid and aniline chloride), and consequently must 
be regarded as suberised. 
It remains now to point out the differences existing between 
the constitution of the cell-walls in the oophyte and sporo- 
phyte of the same Moss and the effect these differences 
have upon the whole life of the organisms. 
In the oophyte, as Oltmanns showed, water is absorbed 
at the external surface of the stem and leaves, consequently 
there is no transpiration-current in the stem. This is pos- 
sible, as my observations show, on account of the absence 
of a cuticle and the slightest trace of cuticularization in 
the external walls. Absorption of water is even made more 
