Slack^ on the Vinegar Plant. 
15 
of disease ; and some observers have argued that the species 
of such organism may be inferred from the conditions under 
which they live and the kind of work they perform. I fear 
that such criteria cannot be relied upon, since, in the experi- 
ments I have detailed,, the same cells have been grown under 
different conditions ; first, in a rich saccharine solution, in 
which the only vinegar present was the small quantity imbibed 
by the gelatinous structure of the plant in its previous posi- 
tion ; secondly, as the fermentation proceeded, they grew in 
a strong vinegar solution, and lastly, they produced the blue, 
green and yellow mould, when both vinegar and sugar had 
disappeared. 
My experiments show that a fragment of vinegar plant taken 
out of the solution in which it was growing and giving rise 
to acetic acid, continues to grow and excite a similar action 
in another solution if quickly transferred to it ; but that if, 
before being put in the second solution, it is dried or exposed 
for some time to the air, its acetifying properties are not 
displayed. Thus the same species of plant, presenting the 
same physical appearance, may differ considerably in the 
chemical actions it can excite, and in its own method of 
growth ; giving rise in one case to fresh co-operative colonies 
of associated cells, in another to crops of blue mould, and in a 
third, to mycelium threads and cells, which do not excite the 
vinegar fermentation. It would, I think, be dangerous to 
conclude that two of these humble organisms must be of 
different species, because they have been grown in different 
fluids, and may be killed by a transference from one to the 
other, and it would be interesting to ascertain under what 
divers circumstances spores of the same plant could be in- 
duced to vegetate, and what varieties of fermentation or other 
actions they could be made to produce. 
