465 
of phenogamic plants, are naked, that is, produced on spicules, and are 
not inclosed in cysts. By general consent, the term spore is limited to 
such germ-cells as are not produced in cysts. Peronospora appears to 
be favored in its growth by excessive moisture, followed by high tem- 
perature. Drainage, shelter, and a moderately moist and warm atmos- 
phere are unfavorable to its growth, and consequently favorable to the 
healthy development of the native grape-vine. 
As to whether grape-rot is a distinct disease, or only a form of mil- 
dew, mycologists generally believe that mildew of the grape-vine is the 
direct cause of the leat-disease, and in some cases may lead to rot of 
the grape; but grape-rot may also be caused by excessive moisture and 
-imperfectly-drained land. 
Mildew is propagated by the spores (seeds) of fungi, which are pro- 
duced in large numbers, and conveyed in the atmosphere to surround- 
ing objects. The spores vegetata with great rapidity on the objects to 
which they are attached, and draw their nourishment principally through 
their mycelium (a form of roots) from the plants on which they grow, 
although a part is derived from the atmosphere. 
Sulphur has generally been relied on as an antidote to mildew, and 
is commonly stipposed to be an antiferment. Whatever its curative 
properties may be in relation to the grape-vine, sulpbur is not an anti- 
ferment as chemically considered; and it cannot be classed as either an 
antiseptic or as a disinfectant, but it may have the power to foster a 
healthy growth of the living plant to which it is applied. 
The following experiment will throw some light on this subject: To 
a pint of pure water I added half an ounce of the flowers of sulphur, and 
immersed in the solution two leaves of a foreign grape-viue. The liquid 
was exposed to a temperature of about 70° Fabrenheit. On the third 
day, fermentation was in full force. On the sixth, the odor of sulpburet- 
ed hydrogen was very strong, bacteria and mycelium of fungi covered 
the whole surface of the water, and the vine-leaves were dec: ayed. L 
have frequently tried this experiment, using various kinds of foliage, 
and have always obtained the same results. 
Some of the compounds of sulphur, as sulphurous acid, dilute sulphurie 
acid, and combinations of sulphur with the alkalies, are of an antifan- 
goid character; but these differ so essentially from the flowers of sulphur 
in their chemical characters that they cannot necessarily be classed with 
that substance. Sulphurous acid has a great affinity for oxygen at ordi- 
nary temperatures, and is easily decomposed, while pure sulphur remains 
unchanged when exposed to the air only. When sulpbur is boiled with 
caustic potash, soda, or lime, sulphides are formed, and such compounds 
are antiferments; but the caustic alkalies mentioned are themselves 
antiferments, and the addition of sulphur will not render them more so. 
Sulpbur in a soluble condi ion may be absorbed by plants as food; and, 
since it is a well-established fact that albumen of both vegetables and 
animals is never free from sulphur, if may be that the application of 
sulphur in a soluble state may indirectly destroy fungoid growths by 
building up the organic structure of the diseased plants, and thus 
enabling them to resist decay by fermentation, which is generally, if 
not always, the result of cryptogamic plants growing on them. 
The specimens of the French Phylloxera vastatrix, alluded to in the 
following letter, have been compared microscopically with the Ameri- 
can Phylloxera vastatrix, and well-defined photographs made of both 
insects. They seem identical. Cuts will be prepared of both for future: 
publication, with such observations as may be made by the entomolo- 
gists of the countries to whom photographs have been sent. 
. 
