Cavers : Some Points in the Biology of Hepaticce. 2 1 3 



in which the whole leaf is made up of numerous fine filaments 

 (e.g-. , Blepharostoma, Trichocolea), or is reduced to two or three 

 such filaments (e.g., Arachniopsis). Amongst many curious 

 forms met with In exotic HepaticEe '"' there may be mentioned 

 Micropterygium , in which each leaf bears a wing or keel similar 

 to that of the moss-genus Fissidens ; Schistochila, in which the 

 leaf is usually provided with several wings of this kind ; 

 Stephaniella, in which the leaf bears numerous green filaments 

 which cover its entire upper surface. In a few forms there is 

 a rudimentary midrib consisting of several rows of elongated 

 cells (e.g., Diplophyllum albicatis, Herbertd) or of a single row of 

 large colourless cells (e.g., Frullanin famarisci, Netirolejeunea) ; 





Fig. II. — Reboulia hemispherica. Part of a transverse section ot the 

 thallus, showing the upper spongy tissue with two pores, and portion of 

 the lower compact tissue with starch-containing cells. X 150. 



but in practically all cases the leaf consists throughout of a 

 single layer of cells, though in a few species it is in part several 

 cells thick (e.g., Schistochila pachyphylld). The division of the 

 leaf into lobes or filaments and the production of filamentous or 

 flattened outgrowths from its surface may be regarded as simple 

 adaptations for retaining moisture, but in many species we find 

 more elaborate modifications to serve the same function. Most 

 of the species in question live as epiphytes on the bark of trees, 

 or, in many exotic forms, cover the leaves of trees with a dense 



* The writer's best thanks are due to Mr. Matthew B. Slater, F.L.S., for 

 many fine specimens of tropical Hepaticae. 



1903 June 



