West : On Mosses. 



3 



to you the separation of the two groups. Mosses develop the sexual 

 generation from the spore with the interventiou of a pro-embrvo. The 

 hepatica^ develop the; sexual generation directly from the spore, or 

 ■with the intervention of a small pro-embryo. The sexual generation 

 of mosses usually has a filiform stem, with leaves in two or more rows, 

 having no bilateral structure, usually monopodial, never dichotomous. 

 The sexual generation in hepaticce is developed as a flat dichotomous 

 stem or thallus, or finally as a filiform stalk furnished with two or 

 four rows of leaves, and usually having one side applied to an object, 

 and when the stem grows erect there is an apparent tendency to form 

 an under as well as an upper surface. The asexual generation of 

 mosses is formed in the calyptra, which is ruptured at the vaginula, 

 and raised by the sporogonium, enveloping the latter as a cup, and 

 the young capsule produces the spores from an inner layer of tissue, 

 the remaining inner tissue is sterile and produces the columella, 

 the wall of the capsule has an epidermis, and it usually divides into an 

 urn-shaped body and a lid. The asexual generation of the hepatica> 

 remains surrounded by the calyptra until the ripening of the spores? 

 the calyptra is then ruptured at the apex, and remains at the base of 

 the sporogonium as a sheath, the spore capsule projects above this 

 sheath and the spores are dispersed ; the mother-cells of the spores 

 arise either from the whole mass of cells composing the capsule, except 

 the outer layer, or the immediate cells usually develope into elaters. 



I shall now confine my remarks to mosses alone. The spore 

 produces a protonema from which the moss, bearing leaves and the 

 sexual organs, arises. The endospore sends out a tube which elongates 

 by apical growth indefinitely, and becomes septate. These form 

 branches close behind the septa, which may produce branches of a 

 higher grade. The part of the endospore opposite the germinating 

 filament may develop into a hyaline rhizoid, which penetrates the 

 ground. The cell-walls of the protonema are at first colourless, but 

 the primary axis, whether laying upon the surface of the ground or 

 penetrating it, soon assumes a brown colour, the right-angled septa of 

 which become oblique. The cells above ground develop chlorophyll 

 grains abundantly, and the protonema is thus nourished in an inde- 

 pendent manner by assimilation. It dies at once in most cases after 

 producing lateral buds ; but in Pottia, Phjscomitrbim^ PJiascmn, &c., 

 it retains its vigour after the development of the sporogonium, and 

 here we have the three stages of the cycle of development presented 

 to us simultaneously in genetic connection. In Spliagimm the spores 

 produce a flat plate of tissue, the margin of which branches, producing 



