14 THE SPHAGNACE& 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. 



The 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 retort cells, more or less 



