W or maid.- — Further Studies of the Frown Rot f Fungi. I. 313 
No. 6. On May 31 the whole shoot was dead and bore withered 
leaves ; pustules of M. cinerea were present on the inoculated leaf. By 
June 4 infection had extended into the twig and there was a globule of 
gum at the node. On June 15 the twig was removed and photographed 
(Fig. 14) ; the canker on the twig was only about 1 cm. in length, but 
necrosis of the young xylem elements, extending beyond the canker for 
0-5 cm. upwards and 4-5 cm. downwards, had taken place as in the case of 
natural infections. Mycelium was found in the brown tissues of the canker, 
and particles of transverse sections through the bark placed on agar plates 
gave rise to typical cultures of Monilia cinerea ; a subculture, on steamed 
potato, from one of these produced grey Monilia fructifications within five 
days. Thus, as in Experiment 1, proof was obtained that the fungus used 
in inoculating the leaf had penetrated into the twig. No mycelium was 
found in the disintegrated xylem beyond the canker, and thick sections, 
taken at 1 cm., 2 cm., and 4 cm. below the canker, placed on agar, showed 
that the fungus was not present, since no growth resulted. 
The browning of the tissues bordering the punctures in Experiment 2 
was apparently the first external symptom of infection, for the punctures on 
the control leaves, on May 11 and later, had pale margins ; on these un- 
inoculated punctured leaves again there was no distortion, showing that 
merely puncturing the leaf does not check its growth on the injured side. 
A comparison with the control leaves therefore shows that infection 
occurred in all the inoculated punctured leaves of that experiment. The 
failure of the infection to extend to the base of the leaf even where definite 
brown areas appeared round the punctures may have been due to (1) the age 
of the leaves when inoculated, or (2) the very dry weather which prevailed 
almost throughout the whole period during which observations were made ; 
in all probability both these factors influenced the result. With regard to 
the age of the leaves it would seem that very young leaves are more 
susceptible than older ones, since the leaves of shoots showing the wilt, when 
naturally infected, are almost invariably quite small when killed ; this, 
together with the fact that, in Experiment 2, the one shoot which was 
eventually killed was almost fully developed when the infection reached the 
axis of the shoot, suggests that, in order to secure results more comparable 
with natural infections, the inoculations must be carried out on still younger 
leaves. 
The falling out of the infected tissues in the majority of the leaves 
suggests that the cells are killed in advance of the hyphae ; it is conceivable 
that such dead cells, rapidly becoming desiccated by the persistent dry 
condition of the atmosphere, would check further growth of the fungus and, 
as the uninfected tissues of the young leaf continued to grow, a line of 
rupture would appear between the dead and the living parts. On the other 
hand, the mere drying out of the infected tissues would tend to inhibit 
