246 Prof, J. B. Farmer. On the Quantitative Differences in the 



water-content in the sapwood, and it becomes a question whether, when the 

 need for seasoned timber is urgent, it may not pay to fell during the summer 

 in spite of the difficulties and disadvantages of so doing. Of course it is the 

 deciduovis trees that most clearly exhibit this kind of difference between the 

 wood in summer and winter. The evergreens are transpiring all the time, 

 and show to a far less extent the striking differences which are here refei-fed 

 to. T have endeavoured to obtain information on this subject from practical 

 foresters and others * interested in woodland industry, but very little appears 

 to be known, at any rate in this country, on the subject. Nevertheless, it 

 would be easy to plan a few test experiments which would settle the matter, 

 and they would also indicate the extent to which different species might lend 

 themselves with advantage to summer felling, or how far the same drying 

 out effect might be obtained by ringing the sapwood during the summer, as 

 is sometimes done. 



In such trees as Birches, Plums, and probably in others as well, it is possible 

 to follow the autumnal filling up of the wood by the water. The lower 

 branches are found to be filled first, and they sink when cut off and thrown 

 on to water whilst those higher up still float. In a well-grown Plum-tree of 

 about 12 years of age more than a week was required from the date at which 

 the lower branches were first observed to sink, before the topmost twigs also 

 ceased to float. The topmost twigs of a large Sycamore which was blown 

 down early in November, 1917, still barely floated, while those formed lower 

 down sank at once. 



Naturally, as the soil becomes colder, the root action falls off, and it is not 

 until the following spring that renewed activity supervenes, often to such an 

 extent as to produce an abundant flow of sap from the stumps of trees felled 

 at that season. It is perhaps to this latter circumstance that the widely 

 spread idea of the wood being comparatively free from water in winter, and 

 that the filling up of the water-conducting tissues is a concomitant of spring, 

 is to be attributed. 



In Central Europe, where the winter is more severe than in this country, 

 R. Hartigf found the Birch to contain the lowest proportion of water at 

 the end of September. From that time a slight rise was observed, which 

 lasted till the middle of February, when a rapid increase occurs, and the 

 curve indicating water-content rose sharply until the latter end of March, 



* In this connection I desire to record my thanks to Mr. Duchesne for his information 

 given from the point of view of a practical forester, and especially to Prof. Augustine 

 Henry, who has most kindly placed me in possession of the chief statements in the 

 literature, the extremely conflicting character of which indicates how little actual 

 knowledge on the subject we at present possess. 



t 'Unters. a. d. forstbotan. Inst. z. Mlinchen,' II. 



