62 Dr David Christison on the [sess. li. 



growth. Thus ou the 30th April 1885, when tlie leaves of the 

 three Hungary oaks were only beginning to expand, the stems 

 had already added an aggregate of half an inch to their girth ; 

 and on the same date on each of the two following years, 

 when the leaf buds were only beginning to burst, the same 

 trees had increased about half an inch in aggregate girth. 

 On the other hand, one sycamore, with leaves half expanded, 

 and another with leaves fully out, had made no increase in 

 girth on 30th April 1885; and even on 31st May, when both 

 trees had long been in full luxuriance of foliage, there was 

 still no increase in" girth. Thus, on the one hand, we have 

 trees in full foliage for several weeks without any increase 

 in girth ; and on the other, trees merely in bud showing a 

 decided growth. These facts point to the conclusion that, in 

 some trees at all events, the initial spring growth may be 

 independent of leaf expansion. 



VI. Pro-portioned Increase in Girth in the First and Second 

 Half of the Growing Season. 



My former observations showed that the majority of the 

 deciduous trees measured grew mainly in the second half of 

 the season, and the majority of the evergreens mainly in 

 the first half of the season. This has continued to be the case 

 since, but it would not be safe to found a general rule on 

 these results, even in regard to trees of their age, as the 

 number of species tested is insufficient. As to younger trees, 

 it seems pi'obable, from experiments commenced this year, 

 that the majority of them will be found to complete their 

 substantial growth earlier than trees of middle or advanced 



age. 



The following Table shows that in nine deciduous species 

 the increase in the second half of the season exceeded, and 

 genei'ally greatly exceeded, the increase in tlic ih'st half of the 

 season; the smallest dill'erence being in the American oak (44 

 and 56 per cent.) and the greatest in the tulip tree (10 and 90 

 per cent.). In two species the rcisult was the o]:)posite. In the 

 h(jrnbeam the difference was slightly in favour of the first 

 half of the season (51 and 49 per cent.), and in the sycamore 

 the difference in the same direction was greater (55 and 45 

 per cent.), but in neither was the excess remarkably great. 



