GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 49 



the deciduous average rose decidedly, — from 40 to 0*58, the evergreens 

 suffered a decided fall, — from - 80 to 0'68. In 1882 the difference was not so 

 remarkable, as the average of both rose, but in the case of the evergreens to 

 much the greater extent of the two. 



I shall endeavour to explain the causes of these differences at the conclu- 

 sion of this paper, under the head of the connection of weather with the growth 

 of wood. 



Sir Robert Christison was inclined to attribute to the oak tribe a greater 

 power of resisting inclement winters than other leaf-shedding trees possessed. 

 At page 84, part iv. of his paper, he states that while leaf-shedding trees in general 

 suffered a reduction of 41 per cent, in their increment in 1879 as compared with 

 1878, seven oaks measured by him lost only 10 per cent. Unfortunately, for 

 various reasons, all these oaks are not available for comparison in subsequent 

 years, but at page 168, part v., he showed that the average increments of fifteen 

 leaf-shedding trees in three successive years down to 1880 were 0"80 in., 0*45 in., 

 and 0'35 in., and that the corresponding numbers for four of the oak tribe were 

 0*82 in., 077 in., 0*54 in., a result still favourable to the oaks, although not so 

 much so as in the previous instance. But if the facts be examined in detail, it 

 is evident that this apparent superiority of the four members of the oak tribe is 

 really due to one of their number — the hardy and quick-growing Hungary oak 

 — and that the other three, although they suffered little loss in 1879, fell off 

 greatly in 1880. It must be considered also that all these trees, with the 

 exception of the hornbeam, which Sir Robert classed with the oaks, are of 

 foreign origin. If we reckon the growth of the hornbeam with that of the only 

 two British oaks whose measurements are at all reliable, the result is most 

 disastrous for our native oaks ; for while their united growth in 1878 was 205 

 in. and in 1879 1*65 in., it was only 0'70 in. in 1880. In these experiments 

 the number of trees may be too small to give thoroughly reliable results, but it 

 certainly seems probable that the foreigners — the Hungary, American, and 

 Turkish oaks— stand severe winters, in our neighbourhood at least, better 

 than our native oaks, the Hungary oak being much the hardiest of ail, 

 while the British oak comes out worse than any other species of tree under 

 observation. 



The yew seems to form an exception to the rule that the increment of wood 

 in evergreen trees continued to decline in 1881, notwithstanding the remarkable 

 rally made in the leaf-shedding class in that year. We have seen that the 

 average growth of all the evergreen trees declined from 0*80 in. in 1880 to 0'68 

 in 1881 ; but if we take the yews alone, five in number, we find that their 

 average growth rose from 0*35 in. in 1880 to 0'40 in 1881. Thus in the wave 

 of decline and rise during the three severe winters they followed the deciduous 

 group, and not their relations the evergreen Pinacese. 



