Note on the Biology of Fegatella conica. 247 
size of the air chamber pore, however, was the same as in Form III. 
The ventral scales were smaller and fewer than in Form III, two 
rows only being produced, one down either side of the midrib. 
Tuberculated rhizoids were present in bundles in the axils of the 
ventral scales, but were growing vertically downwards, not hori¬ 
zontally, approximating to the lower surface of the thallusas in the 
normal form (Fig. 1, 10). The assimilating filaments of the air 
chambers were flask-shaped with broad necks, approximating in 
form those found in Form III. The chloroplasts however, had all 
migrated to the neck, especially the tip (Fig. 1, 11). The ingrowths 
of the cellulose walls of the tuberculated rhizoids were less 
marked than in Forms I, II and III (Fig. 1, 12, 13), and thus, both 
in position and structure, shewed an approximation to the smooth- 
walled type of rhizoid. Chloroplasts were present in the epidermis, 
and were ranged parallel to the surface along the lower walls. 
There were two layers of loosely compacted assimilating cells, 
containing chloroplasts ranged more or less parallel to the surface 
of the thallus. The ventral tissue consisted of large colourless 
storage cells with unthickened walls. There was a complete absence 
of mucilage sacs (Fig. 1, 14). 
The only two members of the Marchantiales which have been 
described as devoid of air chambers and assimilating tissue are 
Monoclea and Dumortiera. Monoclea has never been found with 
air chambers. The habitual absence of air chambers and ventral 
scales, together with the feeble development of the invaginations of 
the cellulose walls in the tuberculated rhizoids has been correlated 
with the hygrophilous habitat of the plant. 1 Dumortiera, however, 
has been found to produce well-developed air chambers under dry 
conditions. Coker 3 found that plants of D. liirsuta growing on 
a porous sandy soil produced air chambers, whilst the same plants 
grown in dripping water shewed no trace of air chambers. In this 
case, therefore, the absence of air chambers is to be correlated with 
the hygrophilous habitat. Coker concluded that the simple form 
of Dumortiera is secondary, and the loss of air chambers is no doubt 
correlated with the semi-aquatic mode of life of this genus. 
Partial reduction of the air chambers has been noted in several 
members of the Marchantiales. Wheldon, 3 speaking of the group 
as a whole, says that under more aquatic conditions the air chambers 
’ F. Cavers. “ The Inter-Relationships of the Bryophyta. Marchantiales.” 
New Phytologist, Vol. 9, 1910, p. 108. 
2 W. C. Coker. Loc. cit. 
* J. A. Wheldon. “Social Groups in the Bryophyta.” Lancashire 
Naturalist, ’ll. 
