Certain Fungi Parasitic on Plants. 
123 
also the dust of the flowers of sulphur on a second lot, each set 
being secured on glass slides, an inch and a half wide by six inches 
long. 
These slides were subjected to moisture and heat, as before, in 
separate jars. After the usual exposure it was observed that the 
same fungus forms of group B appeared on the germinating 
Oidium. 
These results were not expected, as it has been generally sup- 
posed that sulphur is a perfect preventive of fungoid growth. 
This led me to test the effectiveness of sulphur for that purpose. I 
placed in an eight-ounce jar four ounces of pure water, one ounce of 
green peach-leaves, and two ounces of the flowers of sulphur, and 
subjected the whole to a temperature of 75° to 80° Fahr. In three 
days fermentation commenced in full force, giving off a strong 
odour of sulphuretted hydrogen. In the course of ten days the 
leaves were completely destroyed by the fermentation, demonstra- 
ting that, if the flowers of sulphur are anti-fungoid, the beneficial 
results of its application have not been due, as has been sup- 
posed, to its chemical qualities, but probably to its absorption of 
moisture. 
These experiments also go to show that the vine fungus is a 
true parasite, and that it will not fruit when removed from the 
plant on which it grows. A peculiar condition of the atmosphere 
may also be necessary. The Oidium form of the fungus is not 
supposed by mycologists to be a true mould, but merely a condition 
of a species of Erysiphe. Group B represents a theoretical view 
of its supposed condition ; 12, 13, and 14 its stages of fruiting. 
Figs. 14 and 15 are filled with little sacs (asci) containing sporidia, 
which germinate. Fig. 16, group D, represents one of them, and 
17 a branch of mycelium growing from them, on which grows the 
Oidium. 
It is stated on good authority that the fruit of this fungus has 
not been seen on the vine in Europe. In the fall and summer of 
1871, and also 1872, I found specimens of its perfect fruit in great 
profusion on the foreign vine of the grapery of the Department. 
During the last two years, 1873 and 1874, not a single specimen of 
fruit could be found. Late in the fall of 1872 Mr. WilHam 
Saunders, superintendent of the experimental gardens, had all the 
branches of the foreign vines in the grapery painted with a mixture 
of clay and carbolic acid, for the purpose of destroying the fruit of 
the vine fungus. Future observations may show that such treat- 
ment will prevent, in a measure, the ravages of the vine fungus. 
It has long been observed that very dry seasons are favourable to 
the growth of the Erysiphe fungus. Although a hundred foreign 
vines were exposed to the Oidium in the same grapery, very few 
were affected by it during the last season ; and it is observed that 
