POLYMORPHIC FUNGI. 401 
or stages of other forms. It has been proved beyond doubt that 
many species of fungi are truly polymorphic, appearing under dif- 
ferent phases. It is, notwithstanding all this, most premature 
and unjustifiable to conclude, as some have done, that there are 
no good species at all, or that there is no certainty whatever in 
the study. Whilst admitting that many of our old notions have 
been overturned, that what at one time we hardly deemed possible 
has been proved to take place, we are not prepared to go the 
length of some, whose knowledge of the subject falls far short of 
their assumption. It is not very long since that one writer gravely 
asserted his opinion that all the British species of cidium, for 
instance, would be reduced to a single species; that, in fact, there 
was no sound specific distinction between them. This opinion 
originated probably rather in prejudice than as the result of study 
and investigation. Others have lumped together a host of unasso- 
ciated species, without satisfactory evidence, and declared them to 
be only the same thing under different conditions. Hasty general- 
izations in this, as in other cases, produce more harm than good. 
It is exceedingly difficult to trace such minute organisms as 
fungi, especially moulds, and to prove, without doubt, that they 
are conditions, the one of the other. It is easy enough to sow the 
spores of a certain Mucedine on paste, or potato, or any other 
matrix, cover them carefully, and watch the result; then, if the 
common Aspergillus or Penicillium makes its appearance, to some 
minds it is at once conclusive that the said Mucedine is only a 
condition of Aspergillus or Penicillium. Such a conclusion is not 
only rash, but mischievous, and far from the truth. There is no 
evidence that the Aspergillus or Penicilliwm originated from the 
spores of the Mucedine which were sown, but perhaps never ger- 
minated. When two moulds proceed aaewatly from the self- 
same mycelium, judgment may be pronounced too hastily, for the 
mycelium of both may be distinct, though interlaced together ; the 
safest conclusion being based on two forms of fruit when devel- 
oped upon the same thread. Beyond this, there is always room 
for doubt. Hence it will be seen how difficult it is to prove di- 
morphism in moulds under such conditions. In many cases it is 
more presumption than proof. These remarks are not made with 
the view of discrediting the conclusions of such observers as Prof. 
De Bary and the brothers Tulasne, but wee as a caution against 
assuming as fact that which is only conjectur 
fessrs. Tulasne, in their splendid on ey «Selecta Fungorum 
