126 



to the adjoining chart, showing maximum and minimum temperature 

 curves from December 1st to the date of killing each year at Colum- 

 bia and at Koshkonong, and for the year 1908-09 and 1909-10 at 

 Geneva, New York, it will be seen that there was not more warm 

 weather to start the buds preceding the freeze of January 12, 1909 

 at Columbia or that of January 7, 1912, at Koshkonong, than pre- 

 ceding the freeze of February 13, 1905 at Columbia. 



It would hardily seem possible that the buds in either case 

 could have been started into slight growth preceding the freeze. 

 Buds start very slowly even at high temperature early in January. By 

 referring to the chart it will be seen that the low temperature of 

 January, 12, 1909, came suddenly, following high temperature, while 

 that of February 13, 1905, came following forty-two days of rather 

 low temperature. For sixteen days the maximum temperature did 

 not go above the freezing point. 



There seems to be two possible explanations for the greater 

 hardiness of the fruit buds during the seasons like that of 1904-05 

 in Columbia. " It is possible that by long exposure to low temperature 

 the buds develop the ability to withstand lower temperatures. Since 

 freezing to death of plant tissue seems to result from withdrawal of 

 water from the cell, the fact that slow drying out of the tissue (see 

 Table 19) increased the hardiness of the buds would lend weight 

 to this theory. The cells would be greatly desiccated during the 

 period of low temperature which preceded the freeze of February 

 13, 1905. 



The other possible explanation of this greater hardiness of the 

 fruit buds in 1905 is the very slow falling of the temperature (see 

 Table 20). It will be remembered that the greatest harm resulted 

 when the rapid temperature fall occurred for the first fifteen degrees 

 below the freezing point, though rapid temperature fall during the 

 last ten or fifteen degrees before the killing temperature was reached 

 also caused greater killing than where the temperature fell slowly 

 from the freezing point (see Table 21). This station was unable in 

 its laboratory experiments to maintain a continuous low tempera- 

 ture that would approximate temperature conditions that prevailed 

 outside when buds withstood such extremely low temperatures as 

 in February, 1905. However, buds of varieties known to show great- 

 er resistance on such winters were not killed by temperatures that 

 killed buds of varieties like Elberta, known to be tender. The freez- 

 ing tests in the laboratory then were tests of the relative hardiness 

 of the buds, either of different varieties or of the same variety differ- 

 ing in hardiness on account of local conditions. Twigs to freeze 

 were obtained from New York, from South Missouri, and from 



