Brooks . — Observations on the Biology of Botrytis cinerea . 481 
resistance to attack. However, he gives no details of infection under 
these conditions 
In view of the uncertainty attaching to the power of infection of 
Botrytis conidia, the late Professor Marshall Ward suggested to me the 
advisability of investigating the matter again. At the outset of the work 
the growth of the fungus upon different media was tried. The results 
of this may be summarized as follows : — Upon grape extract stiffened 
with gelatine the fungus grew luxuriantly and produced abundant con- 
idiophores of the normal type. Later, the structures known as ‘ organs 
of attachment ’ appeared in great abundance as brown specks, and 
occasionally sclerotia were produced. 
In Klebs’s solution, similarly prepared, the growth was sparse, only 
a few conidiophores of the normal type being produced. ‘ Organs of 
attachment’ were rarely produced, and sclerotia were not observed. It 
was noticed that in succeeding cultures upon this medium the growth 
became somewhat more luxuriant. This points to the possibility of the 
fungus adapting itself in the course of time to a medium which was not 
originally favourable to its growth. 
Upon bouillon with 10 per cent, gelatine the growth was compara- 
tively feeble, and during the first three generations only conidiophores 
bearing microconidia were borne. This is additional evidence of the well- 
known plasticity of Botrytis upon culture media. The microconidial 
form of fructification has been recorded and figured by several observers, 
notably by Istvanffi, who obtained it upon glycerine cultures. In the 
fourth generation of the fungus upon the bouillon medium the growth 
was more luxuriant and the normal conidiophores were produced. It is 
not known whether this change in the mode of reproduction was depen- 
dent upon some alteration in the conditions of experiment, such as 
accounts for the different modes of reproduction in some Algae, as Klebs 
has shown. If this were the case, the alteration must have been a slight 
one, for the cultures were kept in a room where the obvious physical 
factors controlling the growth were the same. It may be that the fungus, 
having become accustomed during three previous generations to the bouillon 
medium, was sufficiently invigorated to produce again the normal type 
of conidiophore. No sclerotia and but few ‘organs of attachment’ were 
formed in the bouillon medium. 
For the infection experiments Lettuce plants were almost exclusively 
used, as these are extremely susceptible to the attacks of Botrytis. When 
growing upon these plants the fungus produces abundant conidiophores 
of the normal type and, later on, sclerotia. At first, attempts were made 
to see whether the spores could directly infect the ordinary leaves. Thus 
spores from the grape extract medium were placed upon the leaves of 
normal plants kept uncovered in a greenhouse. In another series of ex- 
