MILDEW IN PAPER AND PARCHMENTS. 
41 
ON THE CAUSES AND PREVENTIVES OF MILDEW IN PAPER AND 
PARCHMENTS. WITH AN ACCOUNT OF EXPERIMENTS MADE 
ON THE SATURATION OF GROWING WOOD WITH ANTISEPTIC 
CHEMICAL SOLUTIONS. 
By Alfred Gyde, Esq., M. R. C. S. E. 
The author stated, that, owing to the imperfections formerly 
existing in the microscope, little was known of the real nature of 
the class of plants called fungi until within the last few years ; 
but, since the improvements in that instrument, the subject of the 
development, growth and offices of the fungi has received much 
attention. They compose, with the algae and lichens, the class of 
thallogens (Lindley), the algae existing in water, the other two in 
air only. A fungus is a cellular flowerless plant, fructifying sole- 
ly by spores, by which it is propagated, and the methods of attach- 
ment of which are singularly various and beautiful. The fungi 
differ from the lichens and algae in deriving their nourishment from 
the substances on which they grow, instead of from the media in 
which they live. They contain a larger quantity of nitrogen in 
their constitution than vegetables in general do, and the substance 
called " fungine" has a near resemblance to animal matter. Their 
spores are inconceivably numerous and minute, and are diffused 
very widely, developing themselves wherever they find organic 
matter in a fit state. The principle conditions required for their 
growth are moisture, heat, and the presence of oxygen and of elec- 
tricity. No decomposition or development of fungi takes place in 
dry organic matter ; a fact illustrated by the high state of preser- 
vation in which timber has been found after the lapse of centuries, 
as well as by the condition of mummy^cases, bandages, &c, kept 
dry in the hot climate of Egypt. Decay will not take place in a 
temperature below that of the freezing-point of water, nor without 
oxygen ; by excluding which, as contained in the air, meat and 
vegetables may be kept fresh and sweet for many years. 
The action which takes place when moist vegetable substances 
are exposed to oxygen is that of slow combustion (it has been 
called by Liebig " eremacausis") ; the oxygen uniting with the 
wood and liberating a volume equal to itself of carbonic acid, and 
another portion combining with the hydrogen of the wood to form 
water. Decomposition takes place on contact with a body already 
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