EXACT PROGRESSIVE MEASUREMENT OF TREES. 269 



could give an answer confidently, though most of them were 

 inclined to think that, as all such trees wxre covered with 

 perfect leaves, they must continue to form wood in winter, when 

 that season is not unusually harsh. It is not so, however: there 

 is no growth of wood in evergreen trees in this climate in winter 

 and spring. 



4. The crrowth of wood in leaf-sheddino' trees is confined in 

 ordinary years to the three months of June, July, and August. 

 In May their juices are employed in developing their leaves, 

 without which wood cannot be formed. In September the 

 juices are required for forming the buds for the following year, 

 and for ripening the young twig wood. At least I cannot see 

 any other explanation of the undoubted fact, which at first 

 surprised me, that in fine Septembers there is, with very few 

 exceptions, no growth of wood in leaf-shedding trees. It may 

 be presumed that when an unusually favourable spring develops 

 the leaves early in May, this month will be added to the wood- 

 growing months of the 5^ear. But no such spring has occurred 

 since my observations were begun. 



5. In evergreen trees the growth of wood is limited at the 

 end of the season by the same month as leaf-shedding trees ; but 

 many seem to find the advantage of possessing a full foliage at 

 the advent of fine weather, and begin to form new wood a month 

 earlier than leaf-shedding trees, — that is, during the month of 

 May. 



6. In fast-growing trees it is easy to trace their increase from 

 month to month. Thus a thriving young Hungary oak (Qiiercus 

 pannonica, var. conferta), 27'1 inches in girth at 5 feet from the 

 roots, increased from April 30, 1880, to Mav 31, 0'3 ; from 

 May 31 to June 30, 0'4 ; from June 30 to July 31, 0'4; from 

 July 31 to August 31, 03 ; from August 31 to September 30, 

 O'O — in all, 1-4 inches in four months. These increments are 

 easily measurable in a smooth-barked tree, if the simple precau- 

 tions be observed, which will be noticed presently. It will be 

 observed that this fine species added the month of May to the 

 usual period for leaf-shedding trees growing their wood. The 

 reason is that in 1880 its leaves were fairly developed in the 

 middle of May instead of the beginning of June. 



7. Everyone knows that of our acclimatised trees different 

 species are variously influenced by incidental inclement seasons, 

 some being killed outright, others more or less injured in thoir 

 foliage and twigs, and others indifferent to all weathers, excei)t, 

 l)erhaps, the visitation of an Arctic winter. Now, by minute 

 measurement the extent of this influence may be settled with a 

 speed and certainty, and according to a practical scale, unattain- 

 able in any other way. 



The year 1878 was, on t\w whole, favourable to the growth of 



