MOSSES. 65 
its tops—the dead giving birth to the living—until 
at last the fallen trees were completely entombed, 
and a stratum of upwards of twenty feet of solid 
peat, in some instances, deposited above them. 
When, on the other hand, the basin-shaped hol- 
lows were originally occupied by lakes, the Sphag- 
num or bog-moss abounded in the waters, and 
spread so extensively, even from great depths, as 
through course of time to transform the lakes into 
quaking bogs, which, by the accumulation of drift, 
dust, and rubbish, and the decay of the original 
plants and the formation of new, became ulti- 
mately compressed into solid peat, covered upon the 
surface with heather, or a green vesture of grass or 
moss. The Sphagnum or bog-moss by which this 
great change was effected is of a singularly pale, 
almost snowy-white colour, a peculiarity exceed- 
ingly rare among plants, and sometimes attains a 
length of six or seven feet in deep water ; its large 
air-cells imparting the necessary buoyancy to it. 
Its structure is in many respects different from 
that of all other mosses. Its branches are 
fasciculate and disposed around the stem in 
spirals; it has no roots whatever, but floats un- 
attached in an upright position in the water; 
its cell-walls are perforated, and the leaf-cells con- 
tain a well-developed spiral; while the stem is com- 
posed of tissue, which, under the microscope, bears 
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