MOSS DEVELOPMENT. Sif 
spores in a few weeks before the winter. The bog Hypna, on the 
other hand, & gzganteum, H. cordifolium, H. cuspidatum, FH. nitens, 
&c., blossom in August and September, and ripen their spores in 
July of the next year; they often require ten months for the de- 
velopment of their sporogonia. 4. cupressiforme bears in autumn 
at the same time sexual organs and ripe spores, and hence requires 
one year. The same length of time is required for Philonotis, and 
by some species of Bryum 1and some of Polytrichum, which blossom 
in May and June. 
Of the larger natural systematic groups, the Sphagnaceze, or Bog 
Mosses, consisting of one genus, first claim our attention. 
Only when the spores germinate in water is a branched proto- 
nema developed, the usual form being a flat protonemal expansion, 
as in Fig, 12, on which the leaf-buds appear, and which produce 
root-hairs only in the young state. 
The stem, as it increases in strength, produces laterally by the 
side of every fourth leaf, a very much divided branch. These 
tufts of branches form a compact mass at the summit of the stem, 
but lower down are more distant from each other. The leaves 
spring from the stem and the branches from a broad base, with a 
divergence of 2; they are tongue-shaped or apiculate, and are 
composed of two kinds of cells arranged regularly, large broad 
cells and narrow tubular cells running between the former, and 
connected with one another into a net-work. 
The larger cells show irregular narrow spiral bands, also large 
circular holes ; otherwise they are empty and colourless, while the 
tubular cells retain their contents, form chlorophyll granules, and 
thus constitute the functional tissue of the leaf. 
The stems consist of three layers of tissue; an axial cylinder of 
thin-walled parenchymatous cells, enveloped by a layer of thick- 
walled, dotted, prosenchymatous cells, with their walls coloured 
brown, while the epidermal tissue consists of from 1 to 4 broad 
thin-walled empty cells, possessing in Sphagnum cymbifolium spiral 
thickenings and large openings similar to the leaves. 
The colourless cells of the leaves and of the epidermal tissue of 
the stem, serve as a capillary apparatus for the plant, through 
which the water in the bogs in which it grows is raised up and 
carried to the upper parts; hence Sphagnum, which always grows 
erect, are penetrated with water to their very summits like a 
sponge, even when their tufts stand high above the surface of the 
water. 
The antheridia and archegonia are always distributed on different 
branches, and sometimes on different plants when they form large 
distinct patches. ‘They arise on the fascicled branches as long as 
they are near the summit of the primary stem and belong to the 
terminal tuft, and their time of bearing is mostly autumn and winter. 
