228 BOTANICAL GAZETTE [SEPTEMBER 
which almost exactly resemble those found by Leitgeb in D. zrrigua. 
They show beyond a doubt that the thallus of Dumortiera has been 
derived from more complex forms. It seems probable that the com- 
parative darkness of the caves where the plants are found was the 
factor that induced the formation of the papillae, and that the absence 
of surface water was favorable to the development of the air chambers. 
The “delicate appressed pubescence” mentioned by Underwood 
(Gray’s Manual of Botany) as sometimes present on the upper surface 
of D. hirsuta is no doubt the remnants of the air chambers here 
described. 
In his work on the mycorhiza of the Marchantiaceae N. Golenkin’® 
could find no trace of fungus in Dumortiera, although he demonstrated 
it in Preissia, Marchantia sp., Fegatella, and others. I have looked 
carefully for mycorhiza in Dumortiera, but in no case was any found 
in the thallus cells. Fungus threads were often seen running up inside 
the rhizoids, but they were never traced into the living tissue. There 
is no difficulty in finding abundant mycorhiza in Fegatella. 
BLASIA PUSILLA L.—The symbiotic relation of Blasia and Nostoc 
has often been noted, and Leitgeb (of. cit. Heft 1) has given a very 
good description of the structure and origin of the peculiar chambers 
of the Blasia thallus in which the Nostoc lives. He failed, however, 
to get a preparation showing a section of a fully developed chamber 
with contents, and does not give a drawing that shows the contents. 
By pressing out the Nostoc he found that the colony was penetrated 
by clear cells, which he correctly deduces to be branches of the Blasia 
thallus that have arisen from the slime-secreting hair that was present 
in the young stages. As the origin of the branched cells ramifying 
through the Nostoc is so peculiar, I give a drawing (ig. ¢) that illustrates 
this point in a mature Nostoc chamber. There grows up from the floor 
of the chamber a tree-like structure with a single trunk, and from the 
repeated ramifications of this tree the whole colony becomes inter- 
woven with cells which doubtless serve to abstract nourishment from 
the algae. This whole ramifying structure has in all probability come, 
as Leitgeb thought, from the subsequent growth of the slime-secreting 
cell shown in fg. 5, s. 
This cell, in the young stage shown, projects upward into the 
“Blattohr,” as Leitgeb calls it, while at the opening at the base on one 
side the Nostoc enters. This opening is soon closed, and as the cavity 
°Die Mycorhizaahnlichen Bildungen der Marchantiaceen. Flora go? 209-220, 
p. 11. 1902. 
