HEP A TIC2E. 



297 



in contrast to the Foliose Hepaticce belonging to the family of Jungermanniece, the 

 vegetative structure 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 Hepaticce 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. 211, s) 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, while the masses of tissue which lie behind the apical 

 cell in the central line of the shoot grow more slowly in length. Within this depres- 

 sion the terminal branching of the shoot also takes place ; the branches originate 

 from the youngest segments of the apical cell, which, from their position in the 



FIG. 211 —Mttsgeriafurcata ; the right-hand figure seen from the upper, the left-hand figure from the under side ; fH 

 the mid-rib; s,s',s"t\ie apical region ; y.y wing-like expansion formed of a single layer of cells; f'f'fi" its de- 

 velopment by branching (X about 10). 



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

 and form with it a fork (dichotomy). In the angle between the two bifurcations 

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

 are still very short, a projection (Fig. 2\i,f\f") which overtops and separates its 

 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 fiHform stem 

 of the foliose Jungermanniese, 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 an early period 

 below the apex ; the branching is therefore, from 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 



