GROUP II. BRYOPHTTA : HEPATIC^. 319 



which there is either a group of initial cells (Marchantiacese, 

 Anthocerotacese), or a single apical cell (Jungermanniacese). The 

 branching is commonly dichotomous, taking -place in the plane of 

 expansion ; but the development of branches from the ventral 

 surface is constant in several genera. 



The dorsiventral shoot bears numerous unicellular root-hairs 

 on its ventral (lower) surface ; when thalloid it also bears multi- 

 cellular 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 Marchantiese) may be more or less clearly differentiated 

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

 only in some of the Jungermanniacese (Jungermanniacese acrogynse) 

 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 fertilized oosphere 

 (oospore) in the archegonium (see p. 312). It is a sporogonium, 

 which may consist merely of a capsule (Ricciese) ; 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. Marchantiese) ; 

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

 Jungermanniacese), a false foot (epibasal) being in some cases de- 

 veloped 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 following 

 varieties : It is in all cases differentiated into amphithecium and 

 endothecium ; in all, except most Anthocerotaceae, the archesporium 

 is co-extensive with the endothecium ; in the Anthocerotacese, the 

 whole or part of the endothecium constitutes a columella, a feature 

 in which the Anthocerotacese resemble the Musci. 



In the Riccieae, as a rule, the whole archesporium is sporogenous ;. 

 whereas in all other forms some of the archesporial cells are 



