THE STUDY OF MINUTE FUNGI. 327 
factory basis on which to discriminate species in the minute Fungi, 
and this is true even as regards some genera, and it is with a 
faint hope that some of my readers will aid in establishing such 
a basis that I have called their attention to this subject. The prac- 
tical test of a good species is, that it will produce its like, subject 
to variations which are usually limited in degree. Now this test 
has not been applied to any of the species of Valsa, nor, indeed, 
to any of the Sphæriacei; and the observer who will take a spec- 
imen of Valsa stellulata or of any other species, and propagate 
it, watching its development under varying conditions of place, 
moisture and temperature, and honestly and accurately report the 
results, will do more to advance our knowledge of these plants 
than if he had collected and ticketed a thousand or two of them. 
This field is almost entirely unexplored, and I know of no re- 
ported results of culture of any of the Spheeriacei. All that has 
been done has been in a few cases to observe the succession of 
forms and to conclude on the principle of ‘‘ post hoc ergo propter 
hoc” that these forms necessarily belong to the same plant. 
That some of the minute Fungi in the various stages of their 
development assume different forms—so much so that these forms 
have been classed under different orders and classes, there is no 
doubt— but in very few cases have these various stages been made 
out with anything like precision. The Brothers Tulasne, in the 
second volume of their great work, the ‘‘Selecta Fungorum Car- 
pologia,” attempt to specify the various stages and forms of the 
Sphæriacei—and upon these to base a new system of classifica- 
tion. Splendid as is their work, it will very soon be manifest to 
any one who attempts to make use of it to classify species which 
they have not named—and although the book is a thick quarto, it 
does not refer to one-tenth part of the forms known— that it. will 
afford him little or no assistance. 
The attempt at a physiological classification of these organisms 
is as yet premature, the mere morphological classification being 
still so very incomplete, that it is impossible from published de- 
scriptions to identify much more than half of the minute Fungi 
which have been described, while a vast number have been col- 
lected and named which have never been described at all. I do 
not, therefore, recommend the microscopist who proposes to un- 
dertake this study, to try to do more at first than to recognize 
genera, and I furthermore advise him to confine his work for a 
