FUNGI IN CHEESE RIPENING. 99 
or first inoculated into about 100 cubic centimeters of sterile 
water (acidified with 1.5 per cent. of lactic acid usually) and 
this poured into the jar and shaken until all the crackers are 
wet. Various types of ‘‘ milk cracker’’ soften to a pasty mass 
in this moistening process, The best water crackers are not 
very satisfactory, because the mycelium tends to transform 
bread or cracker into a soft gummy mass. ‘The crackers be- 
come overgrown and matted together until they present much 
less actual surface than might be expected. The substitutes 
tried have been excelsior, hay and. sheets of cardboard wet 
with milk or whey. Although some of these have advantages, 
they were on the whole less satisfactory than the ‘‘ water 
crackers.’’ 
So far, therefore, no material has been found so easily pre- 
‘ 
pared and so satisfactory as the ‘‘Schimmelbrot’’ of the Roque- 
fort cheese makers, on account of the very different habit of 
our mold. 
From the point of view of the use of pure cultures the Oid- 
ium lactis is even more troublesome. This mold produces a 
large proportion and in some strains all of its spores as chains 
below the surface of the substratum. For pure culture work 
petri dish cultures have been the only satisfactory means used. 
Its enormously rapid development, however, makes possible 
the propagation of a culture from day to day from the draining 
boards upon which the cheese is made. ‘These become heavily 
coated with a slimy mass of mycelium and spores upon stand- 
ing over night. Direct transfers from them have been used 
with apparently no serious trouble from contamination. In 
fact so capable is the Oidium of self-propagation in dairy work 
that Epstein declares it to be present in all dairy work. A\l- 
though Roger in his published statement does not mention it 
at all, it was found abundant upon the cheese forwarded by 
him to this Station.. We have succeeded by careful work in 
making many cheeses entirely free from Oidium but with the 
ordinary treatment of dairy utensils it appears constantly in 
factory practice. It is practically possible to rely to a consid- 
erable extent upon the ability of the Oidium to propagate itself 
as has hitherto been done in the factories. 
