262 TRANSACTIONS AND PROCEEDINGS OF [Sess. lvi. 



Introductory. 



In March 1883 I communicated to the Eoyal Society of 

 Edinburgh observations on the Girth-Increase of Trees, 

 begun in 1878 by Sir Robert Christison and completed by 

 myself in 1882 ; and in 1887 and 1888 these observations 

 were supplemented by five additional years' results in 

 Papers read by me to this Society. It was then stated that 

 the majority of the selected trees proved to be too old, or 

 too prematurely old, or to have been too seriously affected 

 by the extraordinary low temperatures of the winters 1879— 

 80-81, to yield altogether satisfactory results, and that I in- 

 tended to institute a fresh series of experiments on a 

 younger set of trees, partly of the same but mainly of differ- 

 ent species. The results are now given for the five years 

 1887-1891. 



Experience taught me that to ascertain the laws which 

 govern girth-increase it was necessary to select vigorous trees 

 in a good soil, because, under less favourable conditions, 

 growth is apt to be irregular, and to fall mainly sometimes 

 on the early, sometimes on the late, part of the season. 

 Unfortunately the soil of the Botanic Garden and Arboretum, 

 although varying in quality, is for tlie most part poor and 

 sandy, and notwithstanding the care exercised in selecting 

 my specimens, the results in a considerable number proved 

 disappointing. About half of the thirty-five selected 

 deciduous trees grow in the south shelter belt of the Ar- 

 boretum, where the soil is little better than a sand-bed ; and 

 altliough they looked well at first, in the result they con- 

 trasted unfavourably l)oth as to appearance and amount 

 of increase with the others, the majority of which were in 

 the well-sheltered and richer Iiollow of the east belt. The 

 few trees selected in the Botanic Garden were also favourably 

 situated. But the soil is unfortunately still less suited to 

 the Conifene. Some species grow luxuriantly while quite 

 young, but tliey are apt to fall off very much long l^efore 

 reaching their prime. A few, nevertheless, have thriven to 

 a res])ectal)le size, such as the handsonic yew, No. 41 in my 

 list, now above six f(M!t in girth, jiiid the Scots lir. No. 11, 

 ii(;aily uii^ht fiM^t in 'jiith : but it only serves to ilhistrate tlie 



