60 SIR ROBERT CHRISTISON AND PR CHRISTISON ON THE 



being considerably above average in February and March, while although 

 April was cool it was free from severe frosts. The summer was also of an 

 average character. The foliage was therefore, in general, rich and abundant. 

 Nevertheless there was again a great falling off in the growth of deciduous 

 wood. This Sir Robert attributed to the extraordinary low temperatures of 

 the previous December, succeeding an autumn unfavourable to the ripening of 

 wood and formation of buds. He believed that evergreen trees had also 

 suffered, although not to the same extent ; but I find that he had been deceived 

 by an error in copying his figures, and that their growth in 1880 was almost 

 identical with that of 1879. 



It is not easy to explain why both classes should have suffered a diminution 

 in the growth of wood in 1879, and only the deciduous class a further decline 

 in 1880. In the first of these years the cause of deficiency was no doubt, as 

 Sir Robert believed, the inclement spring and summer, as the cold of the 

 previous winter although prolonged was not remarkably intense ; under these 

 circumstances both classes of trees were unfavourably influenced. In 1880 

 on the other hand the cold of the previous winter was both prolonged and 

 intense, and in all parts of the country its effects were visible in the killing 

 of tender young wood or even of whole trees. It is no wonder then that 

 the deciduous trees showed a marked decline in addition to the serious loss 

 they had suffered in the previous year. But why did the evergreen class 

 escape this further loss ? Possibly the explanation of this difference may 

 be found in the earlier activity of growth in evergreens in spring. In their 

 exposure to the intense frost of winter their circumstances must have 

 been much the same as those of the deciduous class, but their compara- 

 tively early buds would probably come under the influence of the genial March 

 and April to a greater degree than the later buds of the leaf-shedding trees, 

 which, on the other hand, would encounter a rather inclement May. Another 

 cause that may be suggested is that the previous autumn, which was highly 

 unfavourable to the ripening of wood, may have in some way prejudiced the 

 evergreens less than the deciduous trees. That the evergreen trees under 

 observation were not really hardier than the deciduous ones was proved by 

 their fate in the following year. 



The winter of 1880-81 was even more protracted and severe than that of 

 1879-80. Both the lowness of the average temperature and the number of 

 extremely low readings at the Botanic Garden in January, the coldest month of 

 1880-81, were more remarkable than in December, the coldest month of the pre- 

 vious winter. Thus the lowest temperatures recorded in the latter month were 

 1°, 4°, 15°, 17°, 19°, but those of January 1881 were 0°, 4°, 7°, 10°, 11°, 12°, 12°, 12°, 

 13°, 14°. And this greater cold was prolonged far into the spring. On the last 

 day of February and first few days of March 15°, 15°, 18°, and 19° were recorded, 



