GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 55 



hand, the measurements indicate that they stop growing somewhat earlier 

 than the deciduous class. 



Thus Sir Robert Christison's conclusions are substantially confirmed, 

 although the growth of deciduous wood in May is probably of somewhat 

 greater importance than he supposed. It must be remembered, however, that 

 these rules apply only to the neighbourhood of Edinburgh. In the milder 

 climate, aided by a richer soil, of the south-western districts of Britain, where 

 the leaves expand two or three weeks earlier than here, it is to be expected 

 that the growth of wood will also be correspondingly earlier. Other leaf- 

 shedding species besides the Hungary oak may also be found to be exceptional 

 in the early vigour of their growth, as Sir Eobert's observations and my own 

 include but a small proportion of the numerous native and foreign trees which 

 thrive in our islands. 



A greater irregularity in the distribution of the monthly growth of the 

 evergreens as compared with the deciduous trees occurred in all the three 

 years during which monthly measurements were made. Thus, while the July 

 percentages of growth in deciduous trees as shown in Table III., were 31, 31, 

 and 31 in these three years, in the evergreen group they were 30, 18, and 19. In 

 August the differences were still more striking, the respective figures being 

 24, 32, 25 for the deciduous group, and 9, 31, 13 for the evergreen. 



It is remarkable that in 1881 the growth of the six evergreens, which in 

 July amounted to only 18 per cent, of the annual increment, became vigorous 

 again in August, when it reached 31 per cent. The deciduous group seemed 

 to partake in this exceptionally vigorous growth in August 1881, but to a much 

 less degree, the proportions being 31 per cent, for July and 34 per cent, for 

 August. In treating of the influence of weather on the growth of wood I 

 shall endeavour to explain these apparent anomalies. 



2, a. The Months in which the Growth of Wood is most active in Deciduous Trees. 

 Table VI. — Monthly Percentages of Increase in Girth of Deciduous Trees. 





May 



May. June. and 



June. 



July. 



August 



Sept. 



5 Selected deciduous trees, 1880, . 



1881, . 



1882, . 



28 Deciduous trees, 1882, 



12 + 30 = 42 

 35 



21 + 23 = 44 



16 + 26 = 42 



31 

 31 

 31 



35 



24 

 32 

 25 



23 



3 



2 



To elucidate this subject I give in Table VI. the percentage of growth due 

 to each month of the years 1880, 1881, and 1882, in the five originally selected 



