334 PART III. THE CLASSIFICATION OF PLANTS. 



in which it is radial. It is generally thalloid, but is differentiated 

 into stem and leaves in some forms (e.g. foliose Jungermanniaceas). 

 Its growth is effected by an apical growing-point in which there 

 is either a group of initial cells (Marchantiaceae, AnthocerotaceaB), 

 or a single apical cell (Jungermanniaceae). The branching is 

 commonly dichotornous, taking place in the plane of expansion ; 

 but the development of branches from the ventral surface is con- 

 stant in several genera. 



The dorsiventral shoot bears numerous unicellular root-hairs 

 (absent in Haplomitrium) on its ventral (lower) surface ; when 

 thalloid it also bears multicellular scales (ventral scales) on the 

 same surface ; when foliose, it bears on this surface a row of small 

 rudimentary leaves, termed amphigastria, the fully developed 

 foliage-leaves being borne in two lateral rows, one on each flank 

 of the shoot. 



In the great majority of Hepaticae, the sexual organs are borne 

 on the dorsal (upper) surface, either scattered or in groups ; and 

 sometimes upon a specially modified portion of the shoot, termed 

 the receptacle, either sessile or stalked ; in the latter case the shoot 

 (e.g. higher Marchantieae) may be more or less clearly differentiated 

 into a vegetative and a reproductive part (gametophore). It is 

 only in some of the Jungermanniaceae (Jungermanniaceae acro- 

 gynae) that the sexual organs are developed at the apex of the 

 branches of the shoot, a feature in which they approach the Musci. 



The protonema bears but a single adult shoot ; and this, owing 

 to the transitory nature of the protonema, soon becomes an. inde- 

 pendent plant. The plant is generally monoecious, but sometimes 

 dioecious. 



B. The SPOROPHYTE is developed from the fertilised oosphere 

 (oospore) in the archegonium (see p. 329). It is a sporogonium, 

 which may consist merely of a capsule (Riccieae) ; or it may be 

 differentiated into a capsule and a foot (e.g. Anthoceros) ; or into a 

 capsule, a longer or shorter seta, and a foot (e.g. Marchantieas) ; 

 or into a capsule, a seta, and a rudimentary (hypobasal) foot 

 (some Jungermanniaceae), a false foot (epibasal) being in some 

 cases developed from the lower part of the seta. It never grows 

 by means of a two-sided apical cell as it does in the Mosses. 



The internal differentiation of the capsule presents the follow- 

 ing varieties : It is in all cases differentiated into amphithecium 

 and endothecium ; in all, except most Anthoeerotaceas, the arche- 

 sporium is coextensive with the endothecium; in the Antho- 



