14 THE SPHAGNACEZ OR PEAT-MOSSES OF 
constituted of three distinct cell formations, viz. a central pith, 
an intermediate woody cylinder, and an external bark, though, 
of course, these cannot correspond to the parts so named in higher 
plants; it seems, however, more appropriate to regard the stem 
of Sphagnum as consisting of a cylinder, the cells of which are 
soft and succulent in the centre, but become indurated and 
coloured as they approach the exterior, and an investing cuticle 
composed of one to four strata of large, thin, empty cells, not 
inaptly compared by Lindberg to the velamen or spongy cuticle 
investing the roots of epiphytal orchids, which also consists of 
large aeriferous cells. 
The cells of the axis are long and cylindric, with thin colour- 
less walls, and allow the sap to pass freely up to the growing 
point; those of the periphery are narrower, prismatic, and more 
or less lignified by internal deposit on their walls; their colour 
also varies according to the species, and we thus observe them 
in a transverse section of the stem, forming a yellow, brown, red, 
or blackish ring lying immediately under the cuticle; and it is to 
the colour of these cells appearing through the transparent cuticle 
that the tint of the fresh Sphagnum stem is due. 
The cuticular cells are the largest, and instead of receiving 
any deposit they become thinner by age; they are also empty, 
and in some species contain fine spiral threads on their internal 
wall; they are also frequently perforated by foramina, by which 
they readily communicate with each other. 
Tue BRANCHES. 
The branches spring from the growing cone immediately after 
the leaves, in the form of a little obtuse bud at the side of every 
fourth leaf; and when this has attained a height of three cells, 
the rudiments of the branch leaves also protrude themselves at 
the outer side. 
The distinction between the central and peripheral cells of 
the branches is much less complete than in the stem, and the 
cuticular cells only form a single stratum, which is continuous 
with the innermost layer of the stem cuticle when this consists 
of more than one stratum. The cuticular cells of the branches 
are of two forms, as may be readily seen if we strip off the leaves, 
viz. large transparent parenchym cells like those of the stem 
cuticle, and still larger flask-shaped or vetort cells, more or less 
