Ill THE JUNGERMANNIALES ^ 99 



The further development of the spores and elaters corre- 

 sponds with that of the Marchantiacese (Fig. 46), and 

 there is the same method of the development of the thicken- 

 ings upon the walls of the elaters and the spores. In cases 

 where the spores germinate immediately, chlorophyll is devel- 

 oped and no proper exospore is formed, although the outer 

 layer of the cell wall is more or less cuticularised. 



In the germination of the spores Pcllia offers an exception 

 to the other Jungermanniales, in that the spores divide into 

 a multicellular body before they are discharged from the cap- 

 sule. The presence of centrospheres in the dividing nuclei 

 has been demonstrated by Farmer (5), and recently Chamber- 

 lain (2) has studied these bodies very thoroughly in Pellia. 

 The ripe spore here is an oval body which consists of several 

 tiers of cells, the end cells being usually undivided, and the 

 middle ones each consisting of four equal quadrant cells. 

 There is some disagreement as to the earliest stages in the 

 germination and the establishment of the apical growth. Hof- 

 meister ((i), p. 21) states that in P. epiphylla one end cell 

 of the spore grows out into the first rhizoid, while the other 

 develops into the growing point of the young plant. Miiller, 

 N. J. C. ( ( I ), p. 257), on the other hand, states that in P. caly- 

 cina both ends of the spore develop rhizoids wdiile the growing 

 point, which at first has a two-sided apical cell, like that of 

 Metzgeria, arises laterally. 



The germination of the spores of Aneiira has been studied 

 by Kny ( i ) in A. pahnata, and by Leitgeb ( (7) , III., p. 48) in 

 A. pingiiis, which agrees in all respects with the former. The 

 spores, as is usual in the Jungermanniales, have a poorly-de- 

 veloped exospore, and contain chlorophyll when ripe. Before 

 any divisions take place, the spore enlarges to two or three 

 times its original volume, and then elongates and by repeated 

 cross- walls forms a filament of varying length. In the end 

 cell next an inclined wall arises, which is met by another nearly 

 at right angles to it, and thus the two-sided apical cell is 

 established, and the thallus gradually assumes its complete 

 form (Fig. 48, A). 



Connecting the strictly thallose anacrogynous Hepaticae 

 with the foliose acrogynous ones, are a number of most in- 

 structive intermediate forms. Of these Blasia (Fig. 41, F) is 

 perhaps the simplest. Here the margin of the thallus is lobed, 



