120 
Journal of Mycology 
[Vol. 11 
by which others could be certain they were in possession of the 
same species. It is manifestly impracticable to repeat a long 
series of variation experiments with a number of different fungi 
simply as a means of identification of a form sought. It seems, 
therefore, very desirable to present the results of an effort to find 
the simplest means of characterizing species. 
In attempting to develop a method of description which will 
be practicable, I have limited the media used as much as possible. 
Within this limitation attention is directed to such morphological 
and physiological characters of the colonies as seem to be of 
real value. A card on the plan of the bacteriologists’ has been 
prepared for rapid comparison of results. There are abundant 
weaknesses in this method, but it is intended to call attention 
to important and easily observed differences between forms, and 
ample provision is made for the usual complete written descrip¬ 
tion is well. Such description makes necessary the adaptation 
and definition of a set of terms to avoid confusion, and one must 
recognize as well that no set of terms was ever completely satis¬ 
factory to describe living things. If we remember then that 
a series of observations must cover the whole growing and fruiting 
period of the species, perhaps for several generations, we will find 
some such system as I now propose, suggestive at least. 
The characters used may be best examined separately. 
I. Relation to Culture Media. 
i. Fruiting period. 
In studying a series of cultures it may be very readily shown 
that under exactly the same conditions two species may develop 
from the spore to the ripe fruit in very different times. Whether 
this minimum period is the same or different, its relative length 
is fairly constant for the two, and this commonly remains true 
under changed conditions. For example, the Penicillium used 
in ripening Camembert cheese was first separated from contam¬ 
ination by its much slower development than the entirely 
worthless species mixed with it. Similarly the length of the 
period during which spores are produced varies greatly. Some 
species produce spores from a single set of conidiophores in a 
very limited period then die — apparently. Others produce a 
succession of conidiophores from the same mycelium, which re¬ 
quires a much longer period so that the maximum time for 
different species varies from a few days to several weeks on ex¬ 
actly the same media. Whether the limitation of period is due 
to definiteness of life cycle or to excretory products which inhibit 
further growth is unsettled, but the fact of limitation is reasonably 
clear in many species where the substratum is in no way ex¬ 
hausted. 
