8 INTRODUCTION. 



times vcrvsmall, attached to the stem at more or less 

 regular distances, which are termed ainpJiigastria, or 

 stipules (fii^s. 3 to 6). Sometimes they may resemble 

 the true leaves in miniature or they may be 

 totally different, and occasionally they are absent 

 altogether. Mixed with the stipules, on the ventral 

 surface, delicate unicellular radicles will often be 

 observed, which assist in fixing the Hepatic to its 

 matrix or the mosses with which it is intermixed. 

 Theoretically three rows of leaves are present, two 

 lateral, or true leaves, and one ventral, the stipules 

 or amphigastria, the radicles may be regarded 

 morphologically as modified leaves. 



The leaves, whether normal or stipular, are thin 

 simple plates, of a single series of cells, without 

 any distinct central nerve. These cells vary, within 

 certain limits, in different species, such variations 

 being sometimes useful in the discrimination of 



7. 8. 9- 



closely allied species (figs. 7 to 9). In some cases 



these cells project on the margin of the leaves and 



impart a crenulate or minutely serrulate appearance. 



1 n such a case as that of ScapiDiia aspcra the external 



surface of the cells is delicately w^arted, and this 



roughness is especially evident in Lejcimia Rosset- 



iiaiia. It is only rarcl)- thai they are punctate or 



perforate. 



