STRUCTURE OF LIVERWORTS 



271 



often mainly from the region of the midrib ; these rhizoids also 

 function as organs of attachment. 



The underside of the thallus, in many Liverworts, also bears 

 one or more rows of flat overlapping scales (Fig. 149, s.), which 

 are one cell thick, and not uncommonly purplish in colour. 

 Some forms (e.g. Marchantid] exhibit, in the axils of these scales, 



FIG. 147. A leafy Liverwort (Cephalozia bicuspidata) . A, Portion of a 

 plant. B, Sporogonium showing capsule (c.) before dehiscence. C, The 

 same with dehiscent capsule, showing elaters. D, Elaters (el.) and 

 spores (s.).' 



a second type of rhizoid, characterised by possessing a wall 

 with numerous peg-like internal thickenings (Fig. 149, A, B) 

 The capillary channels, between the dense weft of rhizoids and 

 the overlapping scales, are no doubt of importance in the reten- 

 tion of water for use during periods of drought. 



The Liverworts, however, also include leafy types which 

 somewhat resemble Mosses in habit, and, in general, grow in 



