CHAPTER III. 



LEAFY JUNGERMANNLE. 



The transition from the leafless to the leafy Junger- 

 manniae is a very gradual one ; it passes through an un- 

 broken series of gentle intermediate stages. One genus 

 (Diplolacna) which apparently coincides with Aneura in all 

 its vegetative phenomena, except that it has inferior leaves, 

 is followed by the peculiarly formed genus Blasia, whose 

 stem when young exhibits, in transverse section, the form 

 of an ellipse, and when more advanced, is drawn out in 

 breadth so as to become foliaceous a genus whose superior 

 and inferior leaves differ in shape, the former having en- 

 tire, the latter denticulate, margins. Allied to these is the 

 genus Fossombronia, which has a stem only slightly ex- 

 panded, but nevertheless always much flattened on the 

 upper side, and bearing only superior leaves : this genus 

 differs very little in the relative size of its stem and leaves 

 from many of the leafy Jungermannige taken in the most 

 limited sense. 



The most remarkable member of this series of tran- 

 sitional forms is, beyond all question, Blasia pusilla. In 

 perfect shoots, that is to say, shoots bearing bud-recep- 

 tacles, the stem is so much widened that its edges seem 

 to amalgamate with the horizontally-arranged superior 

 leaves ; these leaves have been somewhat generally con- 

 sidered to be, and have been described as, " segments of 

 the flat stem." On the shoots just mentioned it is only 

 the inferior leaves which look really like leaves ; they are 

 denticulate scales on the right and left of the longitudinal rib 

 which protrudes from the under side, and which throws out 

 roots (PL VI, fig. 16). At the upper end of the stem is found 



