627 



contains less water when it is exposed to the frost. A more abundant 

 evaporation removes more heat from the plant and, therefore, heavily 

 watered plants will cool down more than those which are less turgid. 



(c) Effect of Wind. 



Winds can also act favorably inasmuch as a storm begins with warmer 

 weather, which hastens evaporation, thus removing the water from the 

 tissues. Experimental proofs are furnished by Aderhold's experiments^ 

 with artificial rain. In each of six specimens of pears, which had been kept 

 for several months in summer in a "rain chamber," five examples were 

 found, after a winter frost, to be completely frozen and the sixth partially 

 frozen, while of the check plants, which had stood in a dry chamber, only 

 2 were frozen and 4 were uninjured. 



Nevertheless, no general rules can be formed in regard to the action of 

 wind. Each locality has its own special requirements. If, for example, 

 the statement is made that winds act favorably, this refers only to those 

 cases where no such permanent eflfect of the wind is concerned, as is seen 

 on sandy coasts. There the action of the roots is the determinating factor. 

 Even if they do not freeze, they still cannot take up any more water, while 

 the aerial portions still transpire strongly. Plants can directly dry up under 

 such conditions. The discoveries of Hofker-Dortmund" are noteworthy 

 in this connection. He protected the aerial portions less, but covered the 

 soil, which in autumn had been loosened up about his plants, with manure 

 or damp peat mould and watered the evergreen bushes on sunny frosty 

 days. Because of the covering, the frost could not penetrate very far and 

 the roots could constantly supply water to the aerial. portions. In decorative 

 planting, where the finer varieties of conifers are abundantly used, it seems 

 advantageous, in very windy regions, to use the bluegreen forms instead of 

 the pure green ones. Some growers maintain, in fact, that the former are 

 more resistant. 



Care should further be taken that the base of trees or plants, which 

 throughout the year have possibly been protected by a moss growth, piles 

 of leaves, forest litter and the like, are not exposed in the autumn in clear- 

 ing up, etc. It has been found, in fact, that portions of plants matured 

 under the protection of soil or leaves, contain a sap which freezes more 

 easily than that of portions constantly exposed to the air. Sutherst^ has 

 proved this for celery, carrots, and the hearts of cabbage heads. Besides 

 this, even if the constitution of the cell sap is not a determinating factor, 

 at least the transportation of water is decreased in the roots and trunk 



1 Aderhold, R., Versuche liber den Binfluss haufigen Regens auf die Neigung 

 711 r Erkrankung von Kulturpflanzen. Arb. aus der Kais. Biol. Anst. f. Land- u. 

 Forstwirtscliaft. Vol. V, Part 6, 1907. * 



2 Hofker, Windschutz und Winterschutz. Prakt. Ratgeber i. Obst- u. Garten- 

 bau 1907, p. 61. 



3 Sutherst, W. F., Der Gefrierpunkt von Pflanzensaften. Biedermanns Cen- 

 tralbl. 1902, p. 401. 



