May 1905 ] Suggestions from the Study of Dairy Fungi 119 
students it becomes economically necessary to find some means 
of satisfactorily describing the forms we have. 
The method of identifying by hosts or substrata has 
wrought endless confusion. Many of these species are cosmo¬ 
politan and omnivorous in their conidial or hyphomycete form. 
Not only so, but they present morphological adaptations to dif¬ 
ferent substrata. I cannot agree with the author who recently 
described a Fusarium as new, with the plea that the possibility 
of finding it already described involved much labor and anyway 
(translating) “Just as many species of Fusarium are made as 
there are host plants found infested with Fusarium.” Such a 
study to be of value to-day must present both morphology and 
physiological effect under known and easily reproduced condi¬ 
tions. 
But since my specific problem is cultural, and since the 
importance of these organisms is due to their constant presence 
in all cultural work, in the dairy, in the household, in every form 
of manufacture which offers food material to omnivorous or¬ 
ganisms, I set out the definite task of finding to what extent it 
is possible to find reliable diagnostic characters in their relations 
to standard culture media. In the discussion I will draw my 
suggestions from comparative studies of some fifteen species of 
Penicillium. 
Every Penicillium appearing in hundreds of plates in two 
dairy bacteriological laboratories was isolated and studied. Many 
more have been secured from distant laboratories. Series of 
petri-dish cultures representing every form found have been 
made and constantly watched for diagnostic characters. Easily 
confused forms have been grown in parallel cultures for gener¬ 
ation after generation that such differences as appeared should 
be fully tested. The same species has been cultivated on gela¬ 
tine, agar, potato, cheese, milk, caseine, manure, wood, Raulin’s 
fluid, and other special media. Stimulation by acids and alkalies 
and by the excretions of other fungi and bacteria has been tried. 
In spite of all the changes in morphology and effect, due to 
such treatment, a return to the original gelatine has in most cases 
brought with it a remarkably constant return to the same struc¬ 
tures and effects as upon the plates first thoroughly studied. 
In cases of special difficulty several forms are carefully inocu¬ 
lated into one cold poured plate and their positions marked and 
their entire course of development is watched under conditions 
whose uniformity cannot be questioned. Thus the question what 
characters may be depended upon as constant under constant 
conditions, has been kept always in view. This is in direct 
contrast to those special investigations where the authors have 
set themselves to the task of inducing and describing variations 
in particular species. Such studies have commonly given very 
little attention to the problem of furnishing adequate means 
