198 
POPULAE SCIENCE EEVIEW. 
leaves, and fruit is perfected in from fifteen to eighteen hours. 
Since the zoospores are perfected and ready to germinate in 
twenty-four hours from their being placed in water it becomes 
almost impossible to calculate the myriads of fungi that may 
be produced from a single centre. Dr. de Bary has also 
demonstrated that the brown spots so characteristic of the 
disease are a result of the action of the spores or zoospores. 
By placing a quantity of spores in a drop of water on the 
leaves, stems, and tubers under a glass sufficiently air-tight to 
prevent evaporation, he produced the brown spots, and traced 
their progress from the earliest stages. 
There are a few practical conclusions which may be drawn 
from these discoveries. In the first place, it is clearly shown 
by the production of the spots that the fungus is capable of 
causing the disease, a fact which has been disputed, but now 
placed beyond doubt. The inference is, that not only is it 
capable of producing, but is really the cause of the potato 
murrain. With bodies so minute and active as the zoospores, 
there can no longer be difficulty in accounting for their pene- 
trating the tissues of the plant. They are most active and 
productive in wet weather, especially when it is also warm. 
Moisture appears to be essential, and a dry season the greatest 
enemy to the spread of the disease. That bodies so minute 
and subtle should have baffled all efforts to destroy or eradicate, 
is not now surprising. Whether any method will be found 
to contend successfully with it, is now more doubtful than 
ever. A careful re-perusal of the old facts by the aid of this 
new light will tend to the elucidation of much of the mystery 
in which the subject has been involved. All who have 
hitherto been sceptical of the mycological source of one of the 
greatest pests of modern times, should study M. de Bary's 
pamphlet. 
It will be sufficient for our present purpose to state that one 
of the six families into which Fungi are divided for scientific 
purposes is called Hyphomycetes, a name compounded of two 
Greek words signifying “ thread” and “mould” or “fungus,” 
and is applied to this group because the thread-like filaments 
of which they are largely composed is the most prominent 
feature. In this family there are again a number of smaller 
groups called orders, having an equal value to the natural 
orders of flowering plants; and one of these orders called 
Mucedmes has the fertile threads perfectly distinct* from the 
mycelium or spawn. These threads are sometimes simple and 
sometimes branched, they may be articulated or without 
articulations or septa, short or long, erect or creeping, hyaline 
or whitish, mostly free from colour, and are not coated with a 
distinct membrane. The spores are generally simple, some- 
