780 EXPERIMENT STATION RECORD. 



to say, the prolongation of this repose by protecting the plants and the 

 soil from pveinatuie warmth. As external protections, he recommends 

 covering the ground around the plants with earth or snow or mulching. 

 He gives special attention to the smudging of the vineyards, with some 

 historical details. We must refer to the original ^ for the many details 

 which he gives as to the treatment of plants that have been injured 

 by frost. 



Since 18SG the following additions to our knowledge have been 

 published. In 1886 Wollny^ summarized our knowledge of methods 

 of cultivation by which to assist cultivated plants in overcoming 

 unfavorable climatic influences, especially frost. He lays principal 

 stress upon the introduction of hardy varieties and shows that these 

 may be developed by selecting the larger seeds. In general the plant 

 has a greater resistance to frost in proportion as the seed from which 

 it was developed is larger. Again, plants from unripe seeds possess a 

 less resisting power to the frost than those from the developed seed. 

 Again, a seed that develops prematurely in the fall has the greatest 

 danger of suftering during the following winter. Finally, the plants 

 stand the frost better in proportion as the seed is buried less deeply, 

 since the seeds that are sown shallow give rise to the most vigorous 

 plants. 



Detmer ^ finds that perfectly dry grains and fruits exposed to —10^ C. 

 or lower retain their vitality, but that moist fruits and seeds are killed. 

 Ordinary wheat kept at —10° 0. loses much of its energy and speed 

 of growth and is enfeebled apparently in proportion to its moistness. 

 He agrees with Sachs that many plants die under rapid thawing that 

 live under slow thawing, but that certain parts of plants die in conse- 

 quence of freezing alone independently of thawing. 



Kny^ from his experiments as to whether frost acting on the seeds 

 affected the subsequent development of the plant found that seeds 

 of peas, beans, clover, rape, tobacco, and barley, when they were well 

 dried and then divided into 3 groups, (1) those that were frosted, (2) 

 kept cool, and (3) quite warm, and then planted, germinated and devel- 

 oped without any great difference; but seeds that were not well dried 

 were injured by the cold. 



Wollny •'' finds that potatoes are less in number and Aveight when the 

 seed tubers have been long exposed to freezing. 



L. H. Bailey," has .shown the good influence of wind-breaks in 

 agriculture, including their advantages as a protection against freezing. 



Juraelle' shows that although plants cease respiring at very low 



iLautlw'. Jahrb., 15 (1886), pp. 453-60!t. 



^Forscb. Geb. agr. Pbys., 9 (1886), p. 292. 



3 Ibid., 10 (1888), p. 235. ■'Ibid., 11 (1888), p. 122. *Ibid., 12 (1889), p. 398. 



6N. Y. Cornell Sta. Bnl. 9 (E. S. K., 1, p. 276). 



'Forscb. Geb. agr. Pbys., 14 (1891), p. 445. 



