486 Ridler.—Further Observations on the Fungus 
for a few seconds, washed in sterilized distilled water, burst with a sterilized 
needle, and removed by means of the latter to a Petri dish, where its con¬ 
tents were rubbed over the surface of the filter-paper, the young gameto- 
phytes being thus distributed. The dishes were supplied periodically with 
fresh medium, so that the filter-paper was kept damp. The cultures were 
placed in a north window, so that adequate light was obtained without 
direct sunlight. Growth began almost immediately and continued, but, 
owing to overcrowding, the thalli produced were somewhat attenuated, but 
otherwise quite healthy. 
Isolation and inoculation of the fungus. Further attempts were made 
to isolate the fungus from the thallus, but, as before, these were unsuccessful. 
Bernard and Magrou found similar difficulty in isolating the endophytes 
described by them in species of Solanum , and suggested that the ‘ arbus- 
cules ’ are more adapted to a parasitic life than the ‘ pelotons ’ formed by 
the endophytes of the majority of the orchids, and are incapable of 
developing in the autophytic state. 
Attempts were also made to re-inoculate the fungus isolated from the 
sporophyte into uninfected Pcllia plants obtained in the manner described 
above, but these were also unsuccessful. Confirmation that the fungus 
previously isolated is the true endophyte of Pellia is therefore still lacking. 
Observations on the hydrogen-ion concentration. Soil on which Pellia 
epipliylla was growing was obtained from Leigh Woods, Somerset, and its 
hydrogen-ion concentration was measured colorimetrically. Two methods 
were used for obtaining the soil solution—the centrifuge method described 
by Gillespie and Hurst (1917), and the displacement method first described 
by Gola ( 1910 ) and quoted in a paper by Cavers (1914) on ‘ Gola’s Osmotic 
Theory of Edaphism \ The figures obtained from these solutions were 
as follows : 
Soil solution obtained by 
Indicator. 
pH Value. 
Centrifuge method 
Phenol red 
6.8-7-0 
Displacement method 
Phenol red 
6.8-7-0 
Summary. 
* 
1 . The growth and consequent distribution of the fungus in the thallus 
of Pellia epipliylla is restricted, as shown by.the formation of ‘ arbuscules * 
and ‘ sporangioles ’. Some sort of control is thus exerted by the liverwort, 
and the fungus is prevented from becoming harmfully parasitic. 
2 . The fungus undoubtedly obtains food material from the cells of the 
liverwort, in the form of starch which is replaced by oil after the entrance 
of the fungus. It is very doubtful whether the liverwort gains anything by 
the association. It is possible that nutrient substances may be absorbed 
by the fungus from the substratum, as Stahl (1900) suggests, but the con- 
