378 ORGANOGRAPHY. 



the mouth is surrounded by a single row of teeth the Mosses 

 are said to be aploperistomous ; or, when with two rows, they 

 are diploperistomous. The different appearances presented by 

 the teeth, as well as their number and degree of cohesion, form 

 important distinctive characters in the ditferent genera of Mosses. 

 The operculum as already stated, is formed by a projection 

 of the outer layer of the wall of the sporangium. At the point 

 where the operculum separates an elastic ring or annulus is 

 produced, which encircles the mouth of the sporangium. 



In germination, the inner coat of the spore is protruded as 

 a tubular process, which, as it elongates by cell-division, forms 

 a green, cellular, branched mass or pro-thallus, like a Conferva. 

 As described by Berkley, " this mass is very much of the same 

 nature as the mycelium of Fungi, and is called the Protonoma, 

 and is always distinguished by the cells containing chlorophyll. 

 Many spores may concur in the formation of this mass ; but 

 whether more spores than one concur in the formation of a 

 single plant is doubtful. Be this as it may, after a time a little 

 knot or swollen articulation appears upon the threads, which 

 by cell-division, is developed into a leafy shoot, upon which 

 archegonia and antheridia are afterwards developed." 



The archegonium of Mosses is regarded by Henfrey, as 

 quoted by Balfour, " to resemble the so-called ovules of Club- 

 mosses and Pepperworts, — the archegonium giving rise to sporan- 

 giferous individuals. There is thus a compound organism, in 

 which a new individual, forming a second generation, developed 

 after a process of fertilization, remains attached organically to 

 its parent, from which it totally differs in all anatomical and 

 physiological characters. It is an instance of alternation of 

 generations." 



6. HEPATiCACEiE OR LIVERWORTS. — The reproductive or- 

 gans of Liverworts are of two kinds like those of Mosses, 

 to which this order is closely allied ; they are called antheridia, 

 and archegonia or pistillidia, and both kinds may be found on 

 the same plant, or on different plants. 



The antheridia or male organs are variously situated in the 

 different genera of this order ; thus in the leafy plants, they are 

 placed in the axils of leaves, as in some Jungcrmanniie ; in 

 others, they occur in the substance of the frond or thalloid ex- 

 pansion, as in Riccia, Fimbriaria, &c. ; and in others, as in 

 Marchantia, they are found imbedded in the upper surface of 

 peltate or discoid-stalked receptacles (fig. 808, r). The anther- 

 idia arc small, generally shortly stalked, cellular sacs, of an 

 oval, globular, or somewhat flask- shaped form (Jig. 809). Their 

 walls are usually formed of a double layer of cells, surrounding 

 a number of small cells in their interior. When ripe the anther- 

 idium bursts and discharges its contents ; the internal small 

 cells also burst, and each emits a single, very small, spirally 

 wouiid phylozoon or spermatozuid. 



