4§5 
present in Peltia epiphylla , (Li) Cor da. 
common acids, whether in the cold or when heated. In the presence of 
iodine, hyphae, ‘ arbuscules and ‘ sporangioies ’ turn yellow in colour, and 
with chlor-zinc-iodine they become a reddish brown. The mycosin test 
for chitin described by Wisselingh ( 1898 ) was tried, and after this treatment 
the ‘ sporangioies ’, the walls of the hyphae, and the ‘ arbuscules ’ all stained 
a reddish violet with chlor-zinc-iodine, while the cell-walls of the liverwort 
turned blue; a similar result was obtained with iodine and a trace of 
sulphuric acid. The main hyphae continue to ramify in the thallus, but 
the liverwort seems to possess some sort of control over the fungus, the 
nature of which is not exactly known, by which the latter is prevented 
from obtaining too great a hold on the plant and from becoming harmfully 
parasitic. The ‘ arbuscules ’ are not capable of passing from cell to cell, so 
that by their formation the growth of the fungus is restricted. Noel 
Bernard ( 1909 ) compared the condition of such a plant to that of a vac¬ 
cinated animal, and suggested that the plant possessed une immunity 
humorale. 
Although careful observations have been made, no differences have 
been noted in the size, shape, or structures of the nuclei in infected cells as 
compared with the nuclei of cells from which the fungus is absent. The 
only difference observed was in their position. In uninfected cells the 
nuclei are peripheral, whereas in infected cells they are more often in 
a central position in close proximity to the ‘ sporangioies ’ and ‘ arbuscules ’. 
In the case of young thalli infected at one point only, starch is found 
to be present in all the cells except those occupied by the fungus. In 
‘rejuvenation shoots’ infected only at the thallus end, a considerable 
quantity of starch is present, except in the infected region, where there are 
only a few isolated granules. It would seem that the fungus is responsible 
for the absence of starch in the thallus of the fully developed gametophyte 
of Pellia. There is always a considerable amount of oil in the infected 
region, and especially in the swollen vesicles (Fig. i). As a rule no reaction 
is obtained when these are tested with Millon’s reagent, though in one 
instance a definite brick-red coloration resulted. 
S’ 
Culture of the liverwort . The constant occurrence of the fungus in 
the thallus of Pellia epiphylla might seem to indicate an obligate symbiosis 
between the two organisms. Attempts made in 1921 to grow Pellia plants 
from young gametophytes were unsuccessful; growth began, a few cell- 
divisions took place, and one or two rhizoids were produced, but growth 
did not proceed farther. Attempts were made again in the spring of 1922 
when the capsules were mature. The medium employed was a modification 
of Knop’s solution as used by Servettaz ( 1913 ) in his experiments on 
mosses. The cultures were made under sterile conditions in Petri dishes, 
at the bottom of which several rounds of filter-paper were placed. A cap¬ 
sule of Pellia was immersed in a one per cent, mercuric chloride solution 
