DuPLER: AIR CHAMBERS OF REBOULIA 243 
tion is anything more than a close contact.” He adds further, ‘‘no 
instance has been observed where an outgrowth extends downward 
from the epidermis and ends freely in a chamber, and there is no 
adequate evidence that the epidermal cells themselves ever give rise 
to outgrowths.”’ He finds the ‘more deeply situated’’ chambers 
simple and usually without any partitioning cell plates. The 
secondary partitions apparently arise as outgrowths from the 
floor, as one would interpret the statement, ‘‘as the writer 
conceives the process, the growth of the partitions is both hori- 
zontal and vertical, the growth in the latter direction being often 
equalled by the upward growth (accompanied by cell division) 
of the cells forming the floors of the chambers; these in turn remain 
more or less united with one another and with the cells of the 
partitions and in this way form the system of united cell-plates 
in the dorsal chambers.”’ In astudy of the chambers of the female 
receptacle surface outgrowths from the partitions themselves are 
found, but ‘‘in the vegetative thallus such outgrowths evidently 
play a very minor part in the development of the green tissue.” 
Evans concludes further that the increase in size of the chambers 
is due largely to the growth of the bounding cells, differing in this 
respect from Miss Starr in her interpretation of the situation in 
Plagiochasma. Haupt (9) describes the air chambers of Reboulia 
but does not consider the problem of the origin and development 
of the internal partitions. 
With regard to the problem of the origin of the air chambers 
Leitgeb based his theory of the superficial origin by upgrowth on 
a study of the Ricciaceae (12) but later (13, 14) applied it to the 
Marchantiaceae as well. His theory remained unquestioned for 
some time, even in view of his own admission that at least a part 
of the air chambers seemed to arise schizogenously in Reboulia 
and Plagiochasma. Barnes and Land (1) controverted Leitgeb’s 
idea, replacing it by one which accounts for the origin of the air 
chambers in the Marchantiales as “arising invariably by the 
splitting of internal cell walls, usually at the junction of the 
outermost and first internal layer of cells.” Of the forms with 
the Reboulia type of chamber they studied Fimbriaria (probably 
F. echinella Gottsche) and Plagiochasma sp., finding in the former 
that “the primary splitting usually begins between the cells 
