DIV. i BRYOPHYTA 487 



The epidermal cells of the latter project as papillae and constitute a superficial 

 capillary system in which the spermatozoids are conducted to the archegonia. 



The fertilised egg-cell gives rise to a multicellular embryo (Fig. 436 (7), and 

 this, by further division and progressive differentiation, develops into a stalked 

 oval SPOROGONIUM. The capsule of the sporogonium is provided with a wall con- 

 sisting of one layer of cells except at the apex, where it is two-layered ; the cell- walls 

 have thickened bands. The capsule ruptures at the apex, the lid falling off and 

 the wall splitting into a number of recurved teeth. The ripe capsule, before the 

 elongation of the stalk, remains enclosed in the archegonium wall (Fig. 446 D, 

 aw}, which, for a time, keeps pace in its growth with that of the capsule. As 

 the stalk elongates, the archegonial wall or calyptra is broken through and 

 remains behind, as a sheath, at the base of the sporogonium (E, c). The capsule 

 is surrounded also by the pseudo-perianth, an open sac-like envelope which 

 grows, before fertilisation, out of the short stalk of the archegonium (Fig. 436 



FK;. 447. A, lli> in fl.u.i.1" n* ; submerged floating form. B, Riccia natans; land .form. C, 

 Fdccia natans ; floating form with long ventral scales. (Nat. size. B after GOBBEL. C after 



BlSCHOFF.) 



C, pr ; Fig. 446 D, E, p). The capsule contains spores and elaters (Fig. 446 

 F, G}. 



Marchantia was formerly used in the treatment of diseases of the liver ; this 

 fact explains the origin of the name Liverwort. 



The Ricciaceae ( 103 ) exhibit an extensive simplification of the sporogonium and 

 connect on as reduced forms to the more simply constructed Marchantiaceae. The 

 dichotomously-lobed or cleft thallu.s forms small rosettes, and grows on damp or 

 marshy soil. Riccia natans (Fig. 447 C) is found floating, like Duckweed, on the 

 surface of stagnant water. Riccia fluitans, on the other hand, lives wholly sub- 

 merged, and has narrow, more profusely-branching, thalloid segments (Fig. 447 

 A). These two aquatic species can, however, grow on marshy soil, and then form 

 flat rosettes (Fig. 447 B}. The Riccias are provided with fine rhizoids springing 

 from the under side of the thallus, and possess, in addition, a row of transversely 

 disposed ventral scales, consisting of a single layer of cells, which also assist in 

 the absorption of nourishment. Both organs are wanting in the submerged form 

 of Riccia fluitans. 



The antheridia and archegonia are sunk in the surface of the upper side of 

 the thallus. From the fertilised egg-cell is developed a spherical sporogonium 

 which has no stalk. The wall of the sporogonium consists of a single layer 

 of cells ; it becomes disorganised during the ripening of the spores, which are 

 eventually set free by the rupture and disintegration of the venter and the 

 surrounding cells of the thallus. There are no elaters. 



