4 SPHAGNACE^E. 



evaporation and transpiration. In this way extensive tracts of 

 watery country have been "drained" of their moisture, while at 

 the same time the surface has been raised by the constantly 

 accumulating debris of decayed tissue at the base of the plants, 

 thus becoming accessible to and habitable by mankind. The 

 mass of vegetable detritus so formed, when compressed by the 

 weight of growth above it, is often changed into peat; hence the 

 name of Peat-Moss by which the family of Sphagnacese is com- 

 monly known. 



The position and form of the chlorophyllose cells of the 

 branch leaves is of considerable importance in the determina- 

 tion of species. This is best ascertained by cutting thin sections ; 

 but their position, whether dorsal or ventral, may often be 

 ascertained more simply by careful focussing of the leaves, both 

 back and front, with a high power. When the chlorophyllose 

 cell emerges on either side of the leaf, it will appear, viewed from 

 that side, to lie between the two adjacent hyaline cells, the 

 spiral fibres of which will thus be seen to spring from two separate 

 lines, the sides of the chlorophyllose cell, between which the 

 coloured contents of the latter are visible (v. Tab. VI. F.). 

 When, on the other hand, the chlorophyllose cell is enclosed on 

 either face of the leaf by the hyaline cells, the latter, when viewed 

 from that side, will appear to meet in a thin line above the 

 chlorophyllose cell, in such a manner that their spiral fibres appear 

 to spring from this single median line, on each side of which may 

 be seen (on focussing slightly down) the coloured contents of the 

 subjacent chlorophyllose cell (v. Tab. VI. E.). 



Sphagnum Pylaiei Brid., an American species recently found 

 in France and to be looked for in this country, is easily recognised 

 by its stems, simple or with a few branches solitary or in pairs, its 

 broadly ovate leaves similar on the stem and branches, the hyaline 

 cells fibrose but destitute of pores, the chlorophyllose cells wide, 

 almost equalling in breadth the hyaline. 



1. SPHAGNUM. Dill. 

 The only genus. 



j /Branch Is. broad, cucullate, scaly at back of apex 



\ Branch Is. not scaly at apex, rarely cucullate 



s(S™ 1 i 8 T I ° r PUrP ' e 1 ; Cd « with ,r°° th Walls ■■■■ZZZZcymbifi^um 



\ Plant ochraceous ; cell-walls papillose 



2 



3 



