MUSCINE.E. ^„- 



of the spores. Various forms of thickening are not uncommon, especially in the 

 spore-capsule, as in the spiral bands of the elaters of Hepaticse, and the formation 

 of the epidermis and peristome of the thecse of Mosses. 



Classification of Muscinece. The sexual generation is developed from the spore, 

 generally after the previous formation of a pro-embryo. It is the longest-lived of the 

 two generations, and constitutes the self-supporting vegetative structure of these 

 plants, presenting either a flat dichotomously branched thallus, or a thalloid stem, or a 

 filiform stalk furnished with two or four rows of leaves. True fibro-vascular bundles 

 are not produced. The archegonia and antheridia are, except in the simplest thalloid 

 forms, stalked multicellular bodies usually free, but sometimes buried in neighbouring 

 masses of tissue from the subsequent growth of these latter. The central cell of the 

 ventral part of the archegonium produces the oosphere by rejuvenescence of its proto- 

 plasmic body into a primordial cell. The antherozoids are spirally coiled threads with 

 two cilia on the anterior pointed end. 



The asexual generation or sporogonium arises from the oosphere within the actively 

 growing ventral part of the archegonium, which becomes developed into the calyptra. 

 The sporogonium is nourished by the sexual plant; it has therefore no independent 

 existence, and appears externally as an appendage to it. It is usually a stalked cap- 

 sule, in which (with the exception of Archidium) a number of cells are always deve- 

 loped into the mother-cells of the spores ; and from these the spores are formed by 

 division into four after bipartition has commenced but has not been completed. 



(i) Hepaticce. The sexual generation arises either directly from the spore or 

 with the intervention of a small inconsiderable pro-embryo. It is developed as a flat 

 dichotomously branched thallus or a thalloid stem, or finally as a filiform stalk furnished 

 with two or four rows of leaves. This vegetative structure is usually broadly expanded 

 and clings closely to the ground or to some other substratum ; even when the stems 

 grow erect there is still an evident tendency towards the formation of an upper (dorsal) 

 and an under (ventral) surface. The mode of growth is hence always distinctly bilateral. 

 The asexual generation or sporogonium remains surrounded by the calyptra until the 

 spores are ripe ; the calyptra is usually at length ruptured at the apex, and remains at 

 the base of the sporogonium as an open sheath, while the free spore-capsule projects 

 above its apex, to allow the escape of the spores. The mother-cells of the spores arise 

 either from the whole of the cells except those of the single layer which forms the wall 

 of the capsule, or the intermediate cells commonly become developed into elaters. 



(2) Mosses. The sexual generation is developed from the spore with the intervention 

 of a pro-embryo consisting of branched rows of cells and often vegetating for a con- 

 siderable time independently, even when it has already produced leafy stems by lateral 

 budding. The vegetative body is here always a cormophyte, a filiform stem furnished 

 with leaves in two three or four rows, usually without any definitely indicated bilateral 

 structure, and generally branched in a monopodial, never in a dichotomous manner. 

 The asexual generation or sporogonium is only at first formed in the calyptra, after- 

 wards this is usually ruptured below (at the vaginula), and raised up by the apex of 

 the sporogonium, which covers it like a cap. The capsule, which is now first developed, 

 produces the spores from an inner layer of tissue, while a large inner mass of tissue 

 remains sterile, and forms the Columella. The wall of the capsule is covered by a 

 distinctly differentiated epidermis, the upper part of which usually becomes detached 

 from the lower part (the Urn) in the form of a cover, in order to allow the escape of 

 the spores. 



