PREFACE. ix 
in a large new work, Les Microzymas dans leurs rapports avec ’hétérogénie, l’histio- 
génie, la physiologie et la pathologie, Paris, 1883. 
Theories of the kind here described, and others more or less like them, are 
constantly recurring from time to time on the subject of the origin of the Fungi and 
Bacteria. They appeared in earlier times with still greater breadth of application. 
Fifty years ago it was believed that not only minute organisms but that Fungi of the 
size of the Uredineae were produced from the altered substance of other organisms, 
in the case of the Uredineae from phanerogamous plants; two hundred years 
ago maggots were supposed to be bred from putrid flesh. It is easy to understand 
how such ideas of spontaneous generation should have been prevalent in ancient 
times. Even their repeated recurrence in modern times and with our modern know- 
ledge is also capable of explanation. It must be assumed that organisms did once 
come into being of themselves without parents, being produced from organisable but 
not yet organised matter. It must moreover be allowed, that this may still happen at 
any moment and perhaps does actually happen; its impossibility cannot be proved. 
To produce actual proof of an original formation of a living being is a matter of the 
highest interest, and has as powerful attraction for the biological investigator, as the 
prospect of producing the homunculus in the phial for the alchemist. But the 
experience of centuries has shown that whenever the homunculus really appeared in 
the flask, it proved to be a small imp which had been secretly introduced into it from 
without ; and speaking seriously, the result was always of this kind. In every single 
instance exact investigation has shown that the organisms which were supposed to 
have had no parents proceeded from germs produced from parents of the same species 
as themselves; it has also shown how they were formed and whence they came. 
Those who maintained that direct proof had been given of generation without parents 
have been driven back step by step into narrower territory, and upon minuter and at 
last upon the minutest objects, from simple inorganic matter to the organised mini- 
mum, the ‘atome structuré vivant’; in other words they were reduced to seek their proof 
where it is still most difficult to say whether it is to be found or not. This is what 
has happened in all researches into the origin of the Fungi, as soon as each individual 
case was rigidly examined. We have had ocular demonstration of the fact since the 
year 1860, through the labours especially of Pasteur and his school. That there is 
no generation without parents is therefore a maxim of experience; it is in distinct 
accord with the present state of our knowledge, after making allowance for all 
conceivable possibilities, and we must set out from this principle in a book which is 
concerned with real knowledge. 
There is not much to be said by way of preface with regard. to the plan of this 
work. I have endeavoured to make my remarks intelligible even to those who are 
only beginning the study of the Fungi, but I have assumed that my readers are 
masters of such a previous general knowledge of botanical science as is to be obtained 
by a course of study in a University, or by the use of good text-books. The reader 
is here referred to such works, especially to Sachs’ Text-book and Lectures, and 
Goebel’s Outlines, and also to Prantl’s and Luerssen’s smaller compendia, and among 
works not in German to Van Tieghem’s Traité de Botanique. 
A few descriptions only of individual Fungi will be found scattered through the 
volume; others must be sought in our at present imperfect floras, in Saccardo’s 
