146 SECOND GROUP. — MUSCINEAE. 



the higher plants ; Fegatella conica has a thallus traversed by bundles of mucilage- 

 cells ; these cells occur singly in others of the Marchantieae. 



It is not the young Liverwort that proceeds directly from the germinating spore 

 but z. pro tone ma of simple structure, on which the sexual generation then arises as a 

 lateral shoot or in direct continuance of its growth ; in the latter case the sexual gen- 

 eration is not so sharply contrasted with the protonema as it usually is in the Mosses. 

 In Aneiira a tube proceeds from the germinating spore and divides by transverse 

 septa. When several have formed, an oblique wall appears in the terminal cell, and then 

 a second in the opposite direction, and we have the apical cell of the thallus oi Aneiira. 

 The spores of Pellia and sometimes those of Fegatella go through the first stages of 

 germination while still in the sporogonium, as many spores of lichens do inside the 

 ascus. They develope into an ellipsoidal green cellular body with a more transparent 

 cell at one end, and this cell becomes the first rhizoid, while the further development of 

 the young plant begins at its other end. The mode of germination in the foliose 

 species Radula and Fridlania is similar ; the spores are as rsual tinicellular before 

 germination ^ ; the protonema which proceeds from them is a cake-like cell-surface, 

 and the first bud of the leafy stem is formed out of one of the marginal cells. The 

 rest of the foliose forms also proceed from thalloid protonemas. In Lophocolea and 

 Chiloscyphiis the spores have a finely granular exosporium and put out a tube which 

 becomes a cell-row by transverse division. The original walls of the spores can be 

 recognised in a terminal or other cell of the filament thus produced. The rudiment 

 of the young plant is formed in the terminal cell of the filament, which is sometimes 

 also branched. A wall inclined towards the axis of the filament appears in this cell, 

 and commences the formation of the apical cell, which is a three-sided pyramid in 

 the foliose forms. The course of proceeding in the formation of the leaves well 

 deserves notice ; the two lateral rows of leaves first make their appearance, and after 

 them the leaves on the under surface, the amphigastria. The lateral leaves also only 

 gradually acquire their ultimate form; the first are only short cell-rows, the later gradually 

 assume the form of the fully developed leaves. This phenomenon — the appearance 

 of leaves of simpler form in germination — is one of frequent occurrence in the Pha- 

 nerogams. Many other foliose Jungermannieae resemble Lophocolea in these points, 

 only instead of the filaments we find in many of them a protonema of usually irregular 

 shape. The Marchandeae send out a germ-tube which grows towards the light, 

 swells at its apex, and expanding in a direction at right angles to the direction of the 

 light forms a disk, and the young plant developes from marginal cells of this disk. 



The apical region of every shoot lies in most thalloid Hepaticae in an anterior 

 indentation, produced by the more rapid growth in length and breadth of the tissue- 

 cells which have been formed right and left from the segments of the apical cell, 

 where there was one, while the cells lying behind the apical cell in the line of the 

 axis of the shoot grow more slowly in length. The normal branching, which in a 

 great majority of cases is a bifurcation, also takes place within this indentation. The 

 apex first becomes broader, then a central portion of the tissue shoots out before the 

 rest (Fig. 95, il/j, M^, and is known as the middle lobe. In this way the original 

 growing point is divided into two new points, and the middle lobe unites in itself the 



[On spore-structure see Leitgeb, Ueber Bau u. Entwickl. d. Sporenhalite, 1884.] 



