440 BOTANY takt ii 



mother shoot, so that the stem thus becomes falsely bifurcated. By the gradual 

 death of the stem from below upwards the daughter shoots become separated froui it, 

 and form iiidependeut plants. Special branches of the tufted heads are distinguish- 

 able by their different structure and colour ; on these the sexual organs are produced. 

 The male branches give rise, near the leaves, to spherical stalked antheridia, which 

 open at the apices by means of valves ; these bend back and set free the spirally 

 twisted spermatozoids (Fig. 378, E,F). The archegonia are borne at the tips of the 

 female branches. The sjMrogonium develops a short stalk with an expanded foot 

 (B,C), but remains for a time enclosed by the archegouial wall or calyptra. Upon 

 the rupture of the archegonium, the calyptra persists, as in the Hepaticae, at the 

 base of the sporogoniuni. The capsule is spherical and has a dome-shaped columella, 

 which in turn is overarched by a hemisxiherical spore-sac {spo) ; it opens by the 

 removal of an operculum. The ripe sporogoniuni, like that of Andreaea, is borne 

 upon a jirolongation of the stem axis, the pseudopodium, which is expanded at 

 the top to receive the foot of the stalk. Of the peculiar structure of the leaves and 

 stem cortex a description has already been given above. The protonema of the 

 Sphagnaceae is in some respects peculiar. Only a short filament is formed on the 

 germination of the spore, the protonema broadening out almost at once into a flat 

 structure on which the young moss plants arise. 



Order 2. Andreaeaceae 



The Andreaeaceae comprise ouly the one genus, Andreaca, small, brownish 

 caespitose Mosses growing on rocks. The sporogoniuni is also terminal in this 

 order. The capsule, at first provided with a calyptra, splits into four longitudinal 

 valves (schizocarpous), which remain united at the base and apex (Fig. 379). The 

 stalk is short, and is expanded at the base into a foot (Spf), which in turn is 

 borne on a pseudopodium {2->s), a stalk-like prolongation of the stem resulting from 

 its elongation after the fertilisation of the archegonium. 



Order 3. Phaseaeeae 



To the Phaseaeeae (Cleistocarpae) belong small Mosses with few leaves growing 

 on the soil ; they retain their filamentous protoneinata until the capsules are ripe, 

 and have the simplest structure of all the Mosses (Fig. 380). The capsule is 

 terminal and has only a short stalk ; it is protected by a caly})tra. It does not 

 open with a lid, but tlie spores are set free by the decay of its walls. 



Order 4. Bryinae (^'-^) 



In this order (termed also Stegocarpae), which includes the great majority of 

 all the true Mosses, the moss fruit attains its most complicated structure. The 

 ripe SPOiiOGONiUM, developed from the fertilised egg, consists of a long stalk, the 

 SETA (Fig. 38] , s), with a foot at its base, sunk in the tissue of the mother plant, 

 and of a cai'sule, wliich in its young stages is surmounted by a hood or calyptha. 

 The calyptra is thrown off before the spores are ripe. It consists of one or two 

 layers of elongated cells, and originally formed part of the wall of the archegonium 

 which, at first, enclosed tlie embryo, growing in size as it grew, until, finally 

 ruptured by the elongation of the seta, it was carried up as a cap, covering the 

 capsule. In the Liverworts tlie calyptra is, on the contrary, always pierced by 

 the elongating sporoguniuni, and forms a sheath at its base. The upper part of 

 the seta, where it joins tlic capsule, is termed tiie Ai'Oi'llvsis. In MiUuiii (Fig. 



