250 The Water-Conductivity of the Wood in Trees and Shrubs. 



comparison between different stems, whether of the same or different species 

 of plants. 



2. The results obtained throw light on the habit of many " Xerophilous " 

 plants. 



3. The specific conductivity of evergreens is relatively low, with corre- 

 spondingly small absolute fluctuation ; that of the deciduous species (with 

 certain special exceptions) is relatively high, with a fluctuation sometimes 

 relatively high. 



4. Some of the deciduous trees are markedly more plastic and are more 

 easily influenced by environmental conditions than are others. Although 

 this feature occurs in evergreens also, it is far less widespread. 



5. A considerable difference exists between the normal adult wood of the 

 tree and that of " leaders " of young trees, and especially of coppice-shoots. 

 This difference, which is in the direction of a lowering of conductivity, occurs 

 to an exaggerated extent in the main shoot of most climbers. 



6. The wood of arborescent and frutescent monocotyledons is defective as 

 regards water-conductivity, and this is to be regarded as a factor in deter- 

 mining their special habit of growth. 



7. The wood especially of deciduous trees becomes filled up with water 

 during the early autumn, owing to the activity of root pressure which persists 

 after the functional activity of the leaves has ceased. It is suggested that 

 this circumstance may have a practical application in shortening the time 

 normally required for the seasoning of felled timber. 



8. There are grounds for attributing the lower conductivity of evergreens, 

 at least in great part, to the narrow and short vessels which are present in 

 their wood. 



I desire to acknowledge the assistance received from the Department of 

 Scientific and Industrial Research, which has enabled me to secure the 

 services of an assistant, without whose help the work, owing to other demands 

 on my time, could not have been carried on. I also wish to thank my 

 assistant, Mr. H. Tooley, for the conscientious manner in which he has carried 

 out much of the laborious experimental work. 



