ifEPATICM. 



347 



in contrast to the Foliose Hepaticae belonging to the family of Jungermannieae, the 

 vegetative body of which consists of a small slender filiform stem, bearing distinctly 

 differentiated leaves {Jungermannia, Radula, Mastigobryum^ Frullania^Lophocolea, «&c.). 

 Between the thalloid and foliose forms of this family are some which present various 

 stages of transition (as Fossombronia and Blasia). 



The leaves of all Hepaticae are simple plates of cells, in which even the 

 mid-rib usual in the leaves of Mosses is always wanting. 



In most of the thalloid forms the growing apical region of each shoot 

 (Fig. 232, j) lies in an anterior depression, produced by the more rapid growth in 

 length and breadth of the cells which are derived right and left from the seg- 

 ments of the apical cell. In the Anthoceroteae, Riccieae, and Marchanticae, there 

 is a group of apical cells, and the terminal branching is truly dichotomous. In 

 the thalloid Jungermannieae, there is a single apical cell; the terminal branches 

 originate from the youngest segments of this cell, and, from their position in the 



Fig. i-yi.—Metzgeriaftircata; the right-hand figure seen from the upper, the left-hand figure frotn the under 

 side ; tn the mid-rib ; s, s', s" the apical region ; ^y wing-Hke expansion formed of a single layer oicaWs;/'/"/'" 

 its mode of development after branching (X about 10). 



depression and their active growth, push aside the apex of the primary shoot, 

 and form with it a fork (false dichotomy). In the angle between the two bifur- 

 cations the permanent tissue increases more rapidly, and forms, so long as the two 

 forks are still very short, a projection (Fig. 232,/"', y") which overtops and separates 

 the apical regions, but which, when the forks are longer, is in turn overtaken by them, 

 and now appears as an indented angle of the older fork {/). The filiform stem 

 of the foliose Jungermannieae, on the other hand, ends in a bud as a more or less 

 prominent vegetative cone, with a strongly arched apical cell. In this case also the 

 lateral branches spring from individual mother-cells, which, however, do not origi- 

 nate from the youngest segments of the apical cell, but lie, even at their first 

 formation, some distance below the apex; the branching is therefore, at its 

 commencement, distinctly monopodial. 



We shall speak, under the separate sections, of the form of the apical cell, 

 which forms two, three, or four rows of segments; as well as of the origin of the 



