1921] 
WEBB— GERMINATION OF SPORES OF CERTAIN FUNGI 285 
Falck (712) showed that the acidity of the medium is a con- 
ditioning factor for the growth of several species of Merulius. 
'The same writer further observed that Coniophora, by making 
the medium decidedly acid and thus providing favorable condi- 
tions for the germination of the spores, conduced to the sub- 
sequent growth and development of Merulius. 
Peltier (12) obtained best development of Botrytis cinerea 
on various culture media possessing a slightly acid reaction and 
poorest growth on strongly alkaline media. A strongly alkaline 
medium, moreover, caused the mycelium to remain sterile, while 
a strongly acid one reduced the number of sclerotia and favored 
conidial production. 
Stakman (713), in an extensive study on the germination of 
cereal smuts, found that the period required for germination and 
the morphological features during germination varied with the 
organism. In general, greater vigor of germination and more 
abundant and prolonged production of sporidia occurred in 
sugar solutions than in water. 
According to Cooley (714), Sclerotinia cinerea may even grow 
on a medium as acid as the natural juice of sour plums or cherries, 
although it develops more luxuriantly on a somewhat less acid 
medium. Noperceptible growth was immediately produced with 
a neutral reaction of the medium, but at the expiration of 2 weeks 
the mycelial growth at such a reaction nearly equaled that on 
the acid medium. Spore production was very abundant on the 
acid media, but entirely inhibited on the alkaline side. While 
the fungus required relatively high acidity for maximum growth, 
it could adjust itself in time to a slight degree of alkalinity. 
Gillespie (^18) studied the growth of certain strains of Actin- 
omyces chromogenus as related to various hydrogen-ion con- 
centrations within the range Pg 4.8-7.2, using succinate, citrate, 
and potato-tartrate media. In general, the potato-scab organism 
was found to be inhibited in culture media with an acidity of 
Px 5.2, and better growth developed at less acid reactions. 
Individual strains showed different sensitiveness to acidity, but 
the differences failed to furnish any consistent distinctions. 
Growth in the most acid cultures was accompanied by a marked 
decrease of acidity in the medium, but such changes varied with 
the organism, the medium, and the initial reaction. 
