BRYOPHYTES 
93 
i. HEPATICAE 
General character. The liverworts are of great interest on account of 
their apparent relationship to the green algae on the one hand, and to the 
higher plants on the other. Through them the aerial habit of green plants 
seems to have been established. This change in habit involved more 
compact and better protected bodies, and the change from swimming 
spores to aerial spores; but it is important to note that the swimming 
habit was retained by the sperms. Three groups of liverworts are recog- 
nized, each having developed special features: (i) Marchantiales, 
(2) Jungermanniales, and (3) Anthocerotales. 
(i) MARCHANTIALES 
This group may be represented by its two prominent families, Riccia- 
ceae and Marchantiaceae; the former representing the more primitive 
forms, the latter the highly specialized forms. 
Ricciaceae. The genus Riccia (including Ricciocarpus) contains, 
aquatic as well as terrestrial species, so that this family belongs to both 
the water and the land. 
Gametophyte. The gametophyte is a flat, dorsiventral body and 
branches dichotomously (fig. 202). This dorsiventral habit results in a 
differentiation of the body into two 
distinct regions. The dorsal (upper) 
FIG. 202. Riccia: showing 
the dorsiventral, dichotomously 
branching gametophyte, which 
puts out rhizoids and scales from 
its ventral surface; the rows of 
dark bodies in the bottom of the 
conspicuous grooves on the dorsal 
surface are sporophytes, which 
show also the position formerly 
occupied by the archegonia. 
FIG. 203. Riccia: section through dorsal 
region of thallus, showing the intercellular clefts, 
often enlarging into chambers, by means 
of which the cells containing chloroplasts are 
bathed by an internal atmosphere. After 
BARNES and LAND. 
region is composed of green tissue, the intercellular spaces developing 
as numerous deep and narrow clefts, which in some cases broaden 
into chambers (fig. 203), so that all the green cells are bathed by 
