INTRODUCTION. 5 



the spore gives rise to only a single plant ; their 

 protonema is short, usually thick, and very little or 

 not at all branched We need not follow him 

 through the more extended remarks which he offers 

 in support, and his conclusion that the Liverworts 

 seem in their relation to the Mosses to remind us a 

 little of the Dicotyledonous plants in their relation 

 to Monocotyledons. The first and best developed 

 family of Hepaticae is, he thinks, Marchantiacece, 

 with its highest type M, polymorpha ;" and he adds 

 that " the A nthocerotacea must be placed at the end, 

 because their oogonium is naked, and their frond 

 and elaters show a very low grade of development, 

 although they possess a columella, and stomata on 

 the outside of the theca, which two organs are very 

 characteristic, and are vainly to be searched for 

 in the other families of Liverworts. 



VEGETATIVE SYSTEM. 



In general terms it may be said that the Hepa- 

 tics follow two types in their vegetation, they may 

 be frondose as in Marchantiacea, Ricciacece, and a 

 fewjungermanmaag,and then there is a superficial 

 resemblance to Peltigerous Lichens, or they are 

 foliaceous, as in the majority of the Jungcrman- 

 niaccce, and then they resemble mosses ; but in both 

 cases the resemblance is rather superficial than 

 real. In some instances the stem is not wholly 

 obsolete but is fused with the leaf-like expansions 

 into a prostrate frond, being manifested by a 



