properly some care is requisite, for the transverse sections must be
ve ry thin and examined in water by a good light. W e thus find
four modifications of the position of the chlorophyllose cells _
I St. T h e y may lie midway between the anterior and posterior
surfaces of the leaf, being entirely enclosed by the hyaline
cells, and the section shows that the y are lenticularly
compressed.
2nd T h e y may emerge between the hyaline on the anterior or
ventral surface of the leaf, their section being triangular,
so that they resemble a cushion or wedge pushed in
between each pair o f hyaline cells.
3rd. T h e y may occupy the same position on the posterior or
dorsal surface.
4th. T h e y may emerge both in front and back— a condition
observed only in a few species, and in this case their
section is circular or oval. _
T h e hyaline cells are more or less united by their adjacent w alls
and where they are applied to the chlorophyllose cells the walls of
the two become grown together ; in some species this combined
wall, as seen from the interior o f a hyaline cell, is covered over
with minute deposits which take the form o f p a p ife , bars or
crests, and b y some authors have been erroneously described as
remains of spiral fibres ; these are beautifully seen in our 5 . A u s hm
and papillosum, and in the foreign N. Portoricense and Hermimeri.
T h e hyaline cells nearly always contain threads attached to
their internal walls, and these threads may form complete spirals
composed o f one or several fibres, or they may be broken up into
rings and fragments sometimes run across diagonally so as to unite
two ¡piráis ; they are firmly and intimately united to the inner wall
o f the cells, and often, e. g. in N. subsecundum, tightly lace up and
contract the cells at each turn o f the thread, probably by contraction
soon after its deposition. . „ , ,
T h e fibrils are not always present in all the lea v e s ; thus m
S .f im b r ia tum they are wanting in both the stem and perichætial
leaves, and some have them in one half of a stem leaf, as
cuspidatum, where they are found in the upper part but in
5 macrophyllum no threads are found in any part o f the plant.
B y some authors the presence or absence o f threads in the cells
of the stem leaves has been looked upon as o f specific value, bu
a study of the varieties o f the common species .S. acutifolium and
cymbifolium will soon convince any one that it is a character on
which no reliance can be placed. A s the purpose o f the fibres
seems to be to preserve the shape o f the vesicular cells and support
their delicate walls, we should naturally expect to see them most
abundant in the compact or denser forms, and such we find to be
the case, for in the short, close-branched forms o f S. acutifolium the
cells o f the stem leaves are fibrillose throughout, but in the tall,
slender forms they are altogether absent.
T h e pores or foramina stand near the adjacent cell walls, and are
usually found on the posterior surface, but in tenellum they are on
the anterior, and in a few species both front and back are perforated,
as in .S', rigidum. The ir size varies in different sp e c ie s ; thus in
S', acutifolium and cymbifolium they are ve ry large, in S', subsecundum
and cuspidatum ve ry small. Besides these, Russow calls attention
to larger apertures which become visible after treatment with iodine
and sulphuric acid, and indicate more extensive resorption o f the
cell membrane; thus in the lower part o f a branch le a f of
S', fimbriatum so treated, these large openings reach across the
whole width o f the cell. T h e word lumen is applied by continental
authors to denote the clear space in the interior o f a cell through
which light is transmitted, or the space bounded by the internal
lining o f the cells.
In S', fimbriatum, strictum, Lindbergii, and others which have
stem leaves fringed at the apex, this appearance is due to resorption
o f the membrane o f the marginal hyaline cells, and consequent
projection o f the intermediate parenchym cells.
T h e bracts or leaves o f the perichcetium which surround the
elongated receptacle o f the fruit, are much larger than the other
leaves o f the plant, and in areolation are intermediate between
those o f the stem and branches, though coming nearest to the
former; their chlorophyllose cells usually present deficiencies in the
thickening layers o f their walls, and these standing opposite each
other resemble imperforate pits, not unlike the dotted pleurenchyma
o f the wood o f conifers, and a similar condition is observable in the
walls o f young axile cells o f the Sphagnum stem (Hofmeister’s
‘ Higher Cryptogamia,’ pi. xvii. fig. 9 b).
T h e bracts o f the male inflorescence correspond with the branch
leaves in structure, though they are usually broader and sh o r te r ;
but they frequently are adorned in addition with rich colours, which
vary according to the species.