1 66 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY 



and in the United States, but not in Great Britain. Yet such 

 investigations in this country are called for, not only by reason 

 of their physiological and ecological significance, but also 

 because they have a bearing upon the practical problems of the 

 felling season of trees and the seasoning of timber. Mr Craib's 

 paper is therefore particularly welcome. 



His detailed results cannot be readily summarised, but special 

 attention may be directed to his series of facts relating to the 

 sycamore during the " resting " season and opening of the 

 " active " season (October to March). His results appear to 

 indicate that, in the trunk of the sycamore, from October to 

 February, a maximum amount of water lies in the central wood, 

 which in March is so depleted as to become the driest portion ; 

 they showed in the central wood at different heights up the 

 trunk a change of distribution of water from October, when the 

 water showed a decrease in amount upwards, until March, when 

 the reverse had become the case. Again the outer few annual 

 rings contained much water in October, but in the succeeding 

 months a migration of water took place, so that in March the 

 outermost two annual rings were comparatively dry and a 

 maximum amount of water was found just internal to these rings. 

 It is therefore clearly indicated that considerable, and apparently 

 periodic, movements of water take place in the trunk of the 

 sycamore during the winter. Curves and excellent coloured 

 diagrams supplied with Mr Craib's paper graphically record his 

 results concerning the sycamore. Briefer notes are recorded in 

 reference to Platanus acerifolia, Betula verrucosa, and B. pitbescens 

 x verrucosa, Crataegus Oxyaca?itha, Ulmus montana, and Quercus 

 Cerris. 



In interpreting Mr Craib's results, it is necessary to note that 

 the amount of water present in the wood was estimated and 

 recorded as a percentage by weight in reference to the weight 

 of the absolutely dry wood in which the water was originally 

 present. Yet from a physiological standpoint the fundamental 

 feature is the amount of water present in a definite volume of 

 wood. The quantity of water present in a given volume of 

 wood is proportional not only to the percentage (as estimated by 

 weight) present but also to the "specific gravity" of the wood : 

 moreover, if it be assumed that a definite percentage (by weight) 

 of the contained water is held so firmly inside the substance of 

 the lignified walls as to be otherwise unavailable physiologically, 



