A. E. GLBBS-NOTES ON MOSSES. 
69 
the stem, it may appear doubtful whether these are to be considered 
as peculiar forms of the fundamental tissue, or as very rudimentary 
fibro-vascular bundles.* Arguing by the great law of evolution, 
about which these lowly-organised plants teach so much, we should 
expect to find traces of vessels in mosses, for in the stems of the 
plants immediately above them—the club-mosses, pepperworts, and 
horsetails—we find fibro-vascular bundles fully developed. 
I have already referred to the fact that mosses are the lowest 
plants which develope true leaves. These organs are scattered over 
the stem and branches, and consist wholly of parenchyma. In 
shape they generally resemble the leaves of the higher plants, and 
are usually, but not invariably, symmetrical. In some cases they 
are but microscopical in size, yet, though so small, they are none the 
less perfect, and have generally a vein which corresponds with the 
mid-rib of the dicotyledons, of variable length and thickness, which 
occasionally is continued beyond the tip of the leaf and forms a 
hair-like point. A very common moss, Grimmia pulvinata , which 
is to be found on nearly all old walls, growing in glaucous-green 
cushion-like tufts, presents quite a hoary appearance in consequence 
of these hair-like projections being very strongly developed. Some¬ 
times this hair-point is rough and eroded, as in Tortula ruralis. 
The leaf-margin is often serrated, in some cases it is entire, 
in others, as in some species of Mnium , the border is thickened. 
In this last-named genus the leaf-cells are very large and loosely 
placed, and they radiate from the nerve in a very regular and most 
beautiful manner. The leaf-cells of Sphagnum are very in¬ 
teresting objects under the microscope. They are of two kinds, the 
larger ones containing a spiral thread. The structure of the cells, 
the presence or absence of one or more nerves, and the shape and 
margin of the leaf, are very important points to notice in determining 
a species. These leaves are arranged on the stem and branches in a 
regular manner, the same law of phyllotaxis being observed which 
exists in the higher plants. The green colouring is due to the 
chlorophyll which is present in the cells, but no stomates are believed 
to occur in the leaves. 
Mosses are propagated in several ways, the most ordinary of 
which is fructification. Like the higher plants, they are either 
dioecious, monoecious, or polygamous. Instead of effecting fertilisa¬ 
tion by means of stamens, pistils, pollen, and ovules, the mosses 
have other and simpler organs which perform the same functions. 
These somewhat resemble the antheridia and archegonia of ferns, 
and are formed in the axils of leafy shoots. After impregnation the 
sporangium is developed. This is a capsule usually elevated on a 
footstalk or seta, to allow of the escape of the ripe spores; sometimes, 
as m several of the Orthotricha , water-mosses, etc., it is sessile. 
Perhaps the reason that no seta is developed in these Orthotricha 
is that they are tree-growing species, and the spores dropping from the 
capsule are almost certain to fall on the tree trunk in a fit position for 
germination, and therefore it is not necessary that they should be 
* ‘Text-book of Botany," p. 102. 
