4 INTRODUCTION. 



very fragile. When placed in water they recover 

 their form to some extent, but the fugitive colour 

 never returns ; nevertheless they retain their dis- 

 tinctive specific characters, so that there is no 

 difficulty in their determination after the lapse of 

 many years. Although inferior to Mosses and 

 Lichens in bearing the process of desiccation, they 

 are at the same time superior to the fresh-water 

 algae and fungi. What is true of other plants is 

 also true of these — that in order to their complete 

 and accurate determination the fructification is 

 essential. When specimens are collected they 

 should be gathered with their fruit if possible, 

 although there are some species of which the 

 perfect fruit is very rare ; and a few in which the 

 mature capsules have never been found in this 

 country. We do not deny that the experienced 

 hepaticologist would in many cases determine a 

 known species accurately, from other characters, in 

 the absence of fruit when the student would fail. 



The relations of the Hepatics with the Mosses 

 have been the subject of comment by Dr. S. O. 

 Lindberg,* an eminently capable authority, who 

 says that the Mosses are superior to the He- 

 paticae only in regard to the more composite 

 structure of their theca, and the presence of a nerve 

 in their leaf, but in all other respects they seem to 

 be inferior. To which he adds that the Hepaticae 

 are superior to the Bryinece chiefly by the following 

 characters : The polymorphy of all their organs ; 



* Lindberg on Zoopsis, in Linn. Journ. Bot. XIII., p. 196, 1873. 



