head; these sutheridia may be readily obtained by carefully dissecting away the leaves of the catkins, which are usually reddish or brown, and often occur near the summit of the stem. If the autheridia of ordinary mosses are examined microscopically with a ¼ or ⅙ inch objective, they will be seen to contain a number of closely packed cellules, and in each of these cellules a spiral thread-like body may be seen. This spiral body is the antherozoid or fertilising principle of the antherilium; and, supposing that the antheridium is ripe, a very slight pressure of the cover glass will cause it to burst at the apex, and the enclosed cellules will be seen swarming out with a sort of jerky motion, (7 c) In a few minutes the cellulose coat of the cellules is dissolved, and the spiral bodies, the antherozoids, thus liberated, commence moving about in the water, much like some infuseria.
This beautiful sight may be seen readily, and the star-like male flowers of Polytrichum are the most easily examined. These should be got about the end of May or in June. The outer leaves of the flowers should he dissected away, and soma of the ripe antheridia should be examined in water with the 1-10th or pinch objectives.
The archegenia, (9,) (which, with the exception of the Sphagnums, are also surrounded by paraphyses,) are somewhat flask-shaped bodies, the upper part consisting of a slender neck, (9 a,) the lower part being somewhat pear-shaped, (9 b.) In the centre of the pear-shaped body, and near the top, is a small cavity, within which a nucleated cell is developed, called the germinal vesicle, (9 c;) and after the archegonium has acquired some size, a closed canal will he seen passing down the neck, (9 d,) into that part of the pear-shaped body in which the germinal vesicle, (9 c,} is situated, After a while, as growth goes on, the cells bounding the top of the neck fall away, thus leaving an open passage down the canal to the germ cell. Down this canal the antherozoids pass, and reaching at length the germ cell bring about impregnation.
After impregnation has taken place cell-division commences in the germinal vesicle, and continues until by frequent repetition the fruit rudiment is formed. During this time the arckegonium increases in size, the rudiment growing longitudinally, and striking deep down into the base of the archegenitn. This continued upward and downward pressure on the delicate tissues of the archegonium causes it to rupture near the base; the upper part boing carried upwards by the growing fruit rudiment, (10 d,) forms the hood or calyptra, (10 a,) the lower part is left surrounding the base of the rudiment and forming » sheath, which is called the vaginula, (10 e,) (Lat., a little sheath.) At the top of the fruit rudiment the capsule is formed within which the spores are developed.
By virtue of the insertion of the fruit-stalk mosses are divided into two sections, Acrocarpi, or these mosses which have the fruit-stalk terminating the main stem, (4,) as in Pottia truncata, and Plenrocarpi, or those mosses which have the fruit-stalk arising from the side of the stem, (5,) us in Hypnum ratabulum.
The fruit-stalk, which is always present, varies in length; in some cases, as in Phascum serratum, it is very short, in other cases if may he long and conspicuous; it is usually smooth, but sometimes the surface is
