[Vor. 1 
298 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
the writer performed a number of experiments which throw 
more light on the question of the infection of the host. 
Methods and Resulis.—The methods employed were as fol- 
lows: Plum twigs bearing leaves and fruit were broken off and 
brought into the laboratory, washed with a mercuric chloride 
solution (1-1000) and in sterile water. They were then sus- 
pended in sterile moist chambers prepared by placing moistened 
absorbent cotton in the bottom of wide-mouthed one-liter Erlen- 
meyer flasks that had previously been plugged and sterilized. 
Twigs having one or more green leaves were used in every case, 
for in this way green plums hang on the twigs and remain alive 
for some time. This method was especially applicable here, for 
it enabled one to maintain absolutely sterile conditions in а 
moist atmosphere and at the same time keep the host living 
and in a normal condition. Тһе results of these infection ex- 
periments are given in table т. 
Discussion of Results.—From these results it is evident that 
plums were infected as early as June 27, at which time they were 
immature, in fact not more than half-grown. Infection did not 
take place when a spore suspension was placed on very green 
and immature plums unless the epidermis was broken or punc- 
tured. There were, however, some instances where plums re- 
mained healthy in the flask for two or three weeks and became 
infected only after the lapse of time had brought about an 
artificial maturity. On the other hand, plums that were ap- 
proaching maturity, though not mature, as well as mature fruits, 
may be infected by applying a spore suspension to the natural 
surface, i. e., a surface which has not been punctured or injured 
in any way. In this connection it should be mentioned that 
infection was much more readily accomplished when two plums 
were hanging so as to be in contact with each other than when 
they were not touching. This, no doubt, was due to the fact 
that a drop of water containing spores may be held between 
the plums long enough for spore germination and infection to 
take place. These results also indicate that infection takes 
place readily without puncturing when a portion of the mycelial 
felt is laid on the surface of either green or ripe fruit. 
It should be noted here that one can sometimes find plums in 
the field only half-grown which are affected with the brown-rot 
