130 
becomes hard, and this condition prolonged until spring contributes 
much to injure the growth of the plants. The wheat remains low and 
does not head; the meadows yield but little grass, if a spell of warm 
weather does not soon follow so that they may be irrigated, for if the 
wind is dry and cold at the same time watering will do them little 
good. 
(i) Damp warm winds are generally favorable to plants and par- 
ticularly so to various kinds of fodder. Nevertheless, we observe that 
under their action the fertilizing proceeds badly, growth is imper- 
fect, and the maturing is retarded. 
(7) Warm dry winds produce very rapid evaporation, and their 
effect is still more marked if, like the simoon of Arabia, they carry 
with them sand heated by the powerful southern sun. 
(7) Hot dry winds occur, notably along the whole eastern slope of 
the Rocky Mountain Divide, which by their rapid evaporation use up 
all the moisture in the plant and in the soil, causing the plant to 
entirely wilt away. 
THE ORGANIC DUST OF THE ATMOSPHERE. 
IN GENERAL. 
The dust contained in the atmosphere, in so far as it consists of 
organic débris, has a shght influence on agriculture, but in so far as 
it consists of living germs seeking places to rest and grow it is a 
matter of vital importance. Undoubtedly most of the plant diseases 
are spread in all directions by the winds that carry the spores of 
fungi even more widely than they do the seeds of the weeds. But the 
examination of this dust, either by the microscope or by cultivation 
im various appropriate moist media, as also the study of the injuries 
or the good done by the microbes, bacteria, bacilli, micrococci, fungi, 
and other organisms, belongs to vegetable pathology rather than to 
the relations between climates and crops and is a subject so large that 
we must refrain from even attempting to quote the titles of recent 
treatises on the subject by Pasteur, Miquel, Van Tieghem, Koch, Kohn, 
and many other prominent authors in Europe and America. Syste- 
matic daily examination by the culture method of the dust deposited 
from the air had been established at Montsouris under Marié-Davy, 
and at Philadelphia under Dr. J. S. Billings, and will undoubtedly 
do much to explain the dependence of crop diseases upon wind, 
moisture, and temperature. 
WIND AND FORESTS AND GERMS. 
The influence of the forests on the transportation of the micro- 
organisms by the wind has been studied by A. Serafini and J. Arata 
