GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 61 



and another wave of cold brought the thermometer below the freezing point on 

 twelve nights in the first fortnight of April, the lowest readings being 21°, 22°, 

 and 23°. On the other hand, the lowest readings in the same months of 1880 

 were only 23° in February, 22° in March, and 27° in April. Moreover, the total 

 number of nights of frost in these three months in 1880 was only thirty-four, 

 while in the corresponding period of 1881 it was fifty-three. 



After so severe a winter and spring it might have been expected that even 

 more disastrous effects on the growth of wood would have resulted than after 

 the less extreme cold of the previous year. But, on the contrary, the deciduous 

 trees, at least, made a remarkable rally, the average growth of twenty-seven 

 of them having risen from 0'46 in. in 1880 to 0'69 in. in 1881, an increase of 

 nearly one-third. Very different however was the fate of the evergreen trees. 

 Unlike the deciduous class they had successfully resisted the efforts of the 

 previous hard winter, but now they suffered seriously, thus differing once more 

 from the leaf-shedding trees, but in the opposite way, for their average growth, 

 which in 1880 had been 070 in., was now only 0*59 in. 



The wonderful rally made by the leaf-shedding trees in 1881, notwithstanding 

 the almost unprecedentedly low temperatures of the previous winter, can only be 

 accounted for, I believe, by the favourable character of the preceding autumn, 

 which allowed the growth of wood of 1880 to be perfectly matured, and so enabled 

 it to withstand the rigour of the winter in 1881. But why was a similar effect 

 not produced upon the evergreens ? Is it because the maturing of wood is not 

 so effectual with them as it appears to be with the deciduous trees in enabling 

 them to resist a severe winter 1 Or shall we find the reason in the compara- 

 tively early growth of evergreens which might expose their tender buds to the 

 frequent low temperatures of March and April, a danger from which the buds 

 of the deciduous class, coming out later, would be free, while they would benefit 

 by the geniality of May ? The latter seems the most probable cause, but 

 further observations are required to settle the question. 



The winter of 1881-82 was one of the mildest on record. It was well 

 suited therefore to test Sir Robert's suggestion that evergreens might in an 

 unusually mild winter show some trace of growth ; but none could be detected 

 in any of the twenty-eight measured trees. Vegetation however was very 

 early. A sycamore and a Hungary oak among the marked trees in the Botanic 

 Garden began to expand their leaves on the 27th of March. The sycamore 

 paid dearly for its temerity. Caught by an early frost and afterwards attacked 

 by insects, its leaves were irretrievably injured, and its increase in girth for the 

 year only amounted to a twentieth of an inch. A similar fate befell nearly all 

 the horse chestnuts near Edinburgh, including a fine specimen, one of my 

 measured trees, which grew only a tenth of an inch in the year. The Hungary 

 oak, on the other hand, did not suffer at all. The deciduous class as a whole, 



VOL. XXXII. PART I. K 



