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 

 Avind is dry and cold at the same time watering will do them little 

 good. 



{h) Damp warm winds are generally favorable to plants and par- 

 ticularly so to various kinds of fodder. Xevertheless, we observe that 

 under their action the fertilizing proceeds badly, growth is imper- 

 fect, and the maturing is retarded. 



(/) AVarm 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. 



(j) Hot dry winds occur, notably along the whole eastern slope of 

 the Rocky Mountain Divide, Avhich 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 debris, has a slight 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 

 in various appropriate moist media, as al'-o 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 betAveen 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, ^liquel. 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 Marie-Davy, 

 and at Philadelphia under Dr. J. S. Billings, and will undoubtedly 

 do much to explain the dependence of crop diseases upon wdnd, 

 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 



