INTRODUCTION. 3 



Erecto-patent, inakiug an angle witli the stem of about 30°. 



Patent, making an angle with the stem of about 50'. 



Patent-divergent, making an angle with the stem of about 70°. 



Divergent or horizontal, making an angle with the stem of 

 about 90'. 



The cells of the leaves vary in shape and size, having walls 

 clear and well-defined, with angles thickened or not, most fre- 

 quently with smaller cells at their angles, called trigones. 



The following table of sizes of cells, suggested by the late 

 Dr. Spruce, has been used in the present work : 



Comparative Sizes of Leaf-cells of Hepatic.b. 



Large -10 mm. 



Largish or rather large . . •()5 mm. 



Moderate or medium size . 'iy^^t mm. 



Smallish .... 025 mm. 



Small -02 mm. 



Very small or rather minute . -017 mm. 



Minute . . . . -014 mm. 



Very minute . -0125 to -01 mm. 



Texture of Leaves. — In the frondose species the leaves vary 

 from a thin lamina, consisting of a single layer of cells, to thick 

 and fleshy, and numerous cells thick ; in the foliose they are 

 always composed of a single layer, in one or two cases a slight 

 thickening at the base has been observed. Unlike many of the 

 true mosses, they are destitute of a midrib. In one species 

 [Diplophi/Il um albicans) there is a pseudo-nerve, consisting of a 

 line of thickened cells. 



Stipules, or, as they have been called by various authors, 

 amphigastria, and underleaves, are postical leaves usually very 

 small and rudimentary ; in some genera they are large and 

 equalling the leaves and generally of the same texture, but often 

 absent. 



Inflorescence. — The reproductive organs of the Hepatic^! 

 are of two kinds, the male (antheridia) and the female (pistillidia) ; 

 their position affords valuable characters in the determination oi' 

 species. The leaves enclosing them are called 



