82 MOSSES AND FERNS chap. 



the peculiar wing is a dorsal growth (Fig. 32, B, C). Lateral 

 leaf- like appendages are developed on either side of the 

 growing point (Fig. 32, B, C). Both archegonia and antheridia 

 resemble those of SpJicerocarpus very closely, and the structure 

 of the capsule is also the same, no true elaters being developed, 

 but instead these are simply sterile cells. Goebel ^ has 

 recently made some further investigations upon the develop- 

 ment of Riella, and believes that the origin of the growing 

 point is secondary. His view is, however, based upon a study 

 of secondary growths from the young thallus, as he was unable 

 to procure very young germ plants.^ 



Aiieura {Riccardia) and Metzgeria represent the simplest 

 of the typical anacrogynous Jungermanniacese. In the former 

 the thallus is composed of absolutely similar cells, all chloro- 

 phyll-bearing, and in each cell one or more oil bodies, like 

 those of the Marchantiaceae. In Metzgeria (Fig. 33) the wings 

 of the thallus are but one cell thick, and there is a very definite 

 midrib, usually four cells thick. The apical growth in both 

 genera is the same, and is effected by the growth of a " two- 

 sided " apical cell.^ The segmentation is very regular, especially 

 in Metzgej'-ia (Fig. 33), where each of the segments divides 

 first into an inner and an outer cell, the former by subsequent 

 divisions parallel to the surface of the thallus producing the 

 thickened midrib, the outer cells dividing only by perpendic- 

 ular walls, forming the wings. From the ventral surface of the 

 young midrib papillae project, which curve up over the grow- 

 ing point, in the form of short two-celled hairs, whose end cells 

 secrete mucilage for its protection. In Aneura the growth is 

 very similar, but all of the cells divide by walls parallel to 

 the surface of the thallus, and no midrib is formed, and the 

 thallus is several cells thick in all parts. In both genera 

 numerous delicate colourless root -hairs are developed from 

 the ventral surface, especially of the midrib, when that is present. 



Aneura is of interest as showing the only case among 

 the Bryophytes of structures that may be compared to the 

 zoospores of the green Algae. In A. multifida Goebel * dis- 



1 Goebel (14). 



2 On the fertilisation of the archegonium q{ Riella, see Kruch (i). 



•'' "Two-sided" is hardly a strict equivalent for the German " zweischneidig," 

 but will be used here in the same sense, i.e. an apical cell from which two sets of 

 lateral segments are cut off. 



4 Goebel (8), p. 337- 



