DEVELOPMENT OF THE SPOROGONIUM IN THE MOSSES. 267 
layer are thicker than the more external. In longitudinal 
section (Pl. IX. fig. 11) the cells of this tissue show their pecu- 
liar form, being slightly dilated at one, and sometimes at both 
ends. In the latter case these cells may be described as being 
somewhat dumbbeli-shaped. Their transverse walls are not 
usually horizontally placed, and in longitudinal optical section 
have often more or less the appearance of an elongated S (Pl. IX. 
fig. 11). These cells, although they contain granular protoplasm 
and a well-defined nucleus, do not contain any plastids; but they 
contain a number of granules which in many ways resemble those 
described by Janezewski (11) as occurring in the sieve-tubes of 
the Pteridophyta. These granules are stained yellow by (iodized 
zine chloride) Schulze’s solution, brownish-yellow by iodine, 
and bright blue with Hoffmann’s blue. They appear in many 
ways quite distinct from protoplasm, and show no organiza- 
tion. These granules are also frequently found in the cortex, 
notably in that of Dieranum scoparium, Hedw., which contains a 
great number. 
The cell-contents of the leptophloém are generally found aggre- 
gated towards one or other end of the dumbbell-shaped cella, 
thus filling up the dilatation at that end (Pl. IX. fig. 1 1). 
So far all attempts to demonstrate any protoplasmic communi- 
cation between adjacent cells have been fruitless. N evertheless 
some such communication, as has been shown to exist in the case 
of sieve-tubes by Sachs, and in the endosperm of seeds aud 
parenchymatous tissues of the Vasculares by Gardiner (4), 
probably exists in the sporophyte of the Musci. . Certain indi- 
cations of an indirect nature are found in the more persistent 
clinging of the protoplasm to the transverse walls of elongated 
cells after the swelling-up of the cell-wall by Schulzes solution 
(Pl. IX. fig. 12). This observation in itself proves nothing ; but 
the subject is worth further investigation. 
Before leaving this subject it may be well to point out that 
there is no pitting or similar variation in the thickness of any 
of the cell-walls of the sporogonium, except in the case of the 
epidermis of some species of Polytrichum further described 
below. 1 ; 
, Theleptophloém is stained a dull, rather faint blue by Schulze 8 
solution, whereas the leptoxylem is stained a deep bright blue, 
which at once differentiates it from the former. — — 
Passing upwards in Atrichum, the simplicity of its structure, 
