296 MUSCINl/E. 



CLASS IV. 



H EPATIC^\ 



(i) The Sexual Generation is developed, in some genera, directly from the 

 germinating spore, its first divisions resulting in the formation of a cellular lamina 

 or a mass of tissue which fixes itself by root-hairs and produces the thallus by 

 growth at its apex, as in Anthoceros and Pellia. In other cases the embryo which 

 results from the divisions of the spore first forms a narrow ribbon-like lamina of 

 cells, the apical cell of which becomes subsequently the apical cell of a stem, and 

 the segments form leaves, as in Jungermarinia bicuspidaia (according to Hofmeister). 

 Or again, the bud of a leafy stem springs immediately from the spore {Frullania 

 dilatata). In other cases, on the other hand, a pro-embryo is formed; the endospore 

 which grows out into the form of a tube produces a short articulated filament, on 

 which the rudiments of the thallus are formed as lateral shoots, in a manner similar 

 to the leaf-buds of Mosses on the protonema {e. g. Aneura palmata, Marchantia). 

 In Radula the spore produces first of all a cake-shaped plate of cells, from which 

 the first bud of the leafy stem shoots laterally (Hofmeister). 



The vegetative structure of Hepaticse is always formed in a distinctly bilateral 

 manner; its free side, turned towards the light, is differently organised from that 

 which faces and often clings closely to the substratum and is not exposed to light. 



In the greater number of families and genera the vegetative structure is a broad, 

 flat, or curled plate of tissue, varying in length from a few millimetres to several 

 centimetres ; and is either a true thallus without any formation of leaves, as in 

 Anthoceros, Metzgeria, and Aneura, or lamellaeform outgrowths arise on the under 

 or shady side, which at the same time produces root-hairs ; and these outgrowths 

 may be looked on as leaves. For the sake of having a common expression for these 

 forms extremely similar in habit, they may be comprised in the term Thalloid^, 



^ Mirbel, Ueber Marchantia, in the Mem. de I'Acad. des Sci. de I'lnst. de France, vol. XIII, 

 1835.— G. W. Bischoff, in Nova Acta Acad. Leopold. Carol. 1835, vol. XVII. pt. 2.— C. M. Gottsche, 

 ditto, vol. XX, pt. I. — Gottsche, Lindenberg u. Esenbeck, Synopsia Hepaticarum, Niirnberg, 1844. 

 Hofmeister, Vergleich. Untersuchungen, 185 1. — [On the Germination, Development, and Fructifica- 

 tion of the Higher Cryptogamia : Ray Society, 1862.] — Kny, Entwickelung der laubigen Lebermoose ; 

 Jahrb. fiir wiss. Bot. vol. IV, p. 66, and Entwickelung der Riccien, ditto, vol. V, p. 359. — Thuret, in 

 Annal. des Sci. Nat. 1851, vol. XVI (Antheridia). — Strasburger, Geschlechtsorgane u. Befruchtung bei 

 Marchantia ; Jahrb. fiir wiss. Bot, vol. VII, p. 409. — Leitgeb, Wachsthumsgeschichte der Radula 

 complicata; Sitzungsber. der Wiener Acad. 1871, vol. LXIII. — Ditto, Bot. Zeitg. 1871, no. 34, and 

 1872, no. 3. — A portion of what is said about the apical growth of Jungermanniere is derived from 

 communications by letter from Leitgeb. 



^ [The term ' thalloid' is here, as on p. 292, preferred to the one in more general use ' fron- 

 dose.' — Ed.] 



