129 



done in other countries with the same eharaeteristics both of soil and 

 elimate. (See American Meteorological Journal, 1891, Vol. VII, p. 

 41.) 



WIND. 



The effect of the wind on vegetatit>n is quite various. Among other 

 influences, we note the following: 



(«) It is considered that the mechanical action of the motion of the 

 stems and trunks and stalks is to strengthen them and to stimulate 

 the growth of the roots. 



(b) The winds distribute the pollen and the seed and thus assist, 

 or even entirely control, the preservation of the plant and its geo- 

 graphical distribution. 



(/■) The wind renews the air, so that a superabundance of the 

 necessary gases is then assured. 



{(I) During cool, clear nights a wind, by renewing the supply of 

 heat, prevents the fonnation of frosts by radiation. 



{e) On dry, cold, frosty nights the wind, by its dryness, evaporates 

 any frost that may be formed upon the plant, but does not prevent 

 the freezing of the plant as a whole. 



(/) By bringing moisture, fog, and clouds from the lakes and 

 ocean up over the fields and forests the Avind prevents frosts and 

 favors the growth of delicate plants on the leeward side of large 

 masses of water. 



(ff) Gasparin states that when a cold, dry north wind suddenly 

 l)lows over plants in active groAvth they become stunted, and it is 

 said that the plants have taken cold. A similar phenomenon occurs 

 in the valleys of California. 



Gasparin's description is as follows (Cours d'Agriculture, 2d ed., 

 1852, p. 202) : 



In the valley of the Khone the north wind produces a lowering of 

 the normal temperature of about 7° ; all the vegetation is more or less 

 involved if after several days of calm, clear weather, during which 

 the heat has increased, such lowering of temperature is experienced. 

 P^ven if there has been no frost and the plants have preserved their 

 vitality unimpaired, it produces a singular effect on them ; their growth 

 stops and they remain stunted. Our agriculturists describe this con- 

 dition by saying that the plants have ''taken cold." The leaf buds 

 which put out later resume their growth, but the leaves and branches' 

 experiencing this cessation of growth never entirely recover from it. 

 This accident is especially injurious to natural and artificial meadows 

 and to the leaves of the mulberry tree. As regards the meadows, 

 the best thing to do is to hasten the mowing of the grass, in order to 

 gain time for the succeeding crops to prosper, and for the nniUierrv 

 trees it is advisable to await the development of new buds. 



The more rapid these dry winds are the more tliey hasten the drying 

 up of the soil. After they have prevailed for several days the earth 

 2667—05 M 9 



