TRANSACTIONS OF SECTION K. 337 



and mathematiccal treatment could follow later, biit the inclusion in the first 

 year of the above interesting and important topics, treated experimentally, 

 would ensure that students not proceeding further with biology would at least 

 have had their attention directed to some of the most fundamental considerations 

 applicable to the living world around them, while students continuing biological 

 courses would have received timely assistance for which they, and their teachers, 

 would have real cause to be grateful. 



Clearly all that is necess'ary for the achievement of such a desirable object is 

 close and sympathetic co-operation between all University science teachers. As 

 far as individual colleges, &c., are concerned there is no valid reason why this 

 could not be secured almost immediately, for by occasional meetings of the full 

 staffs it couW readily be ascertained what are the special aims, working re- 

 quirements, and points of contact of the several branches of science representee' 

 or about to be represented, in the curriculum. 



In the afternoon a Sectional Excursion took place to Shell Bay. 



THURSDAY, SEPTEMBER 11. 



The following Paper was read : — 



Root Pressure. By Professor J. H. Peiestley, B.Sc. 



An attempt is made to show that in the literature of this subject there already 

 exists the data for a theory of the mechanism of root pressure which woxdd 

 appear reasonably adequate. 



This theory would enlist the services in the mechanism of root pressure of 

 (1) osmosis for the diffusion of water from root hair to the parenchyma bordering 

 on the xylem ; (2) the structure of the endodermis ; (3) the behaviour of a colloid 

 gel in respect to its varying permeability towards water. 



It is suggested that this theory should be acceptable for the moment as 

 embodying the least amount of unverifiable hypothesis, and it is pointed out 

 that it indicates the need for a considerable amount of further anatomical and 

 physiological research. 



Joint Discussion vjith Section M on Forestry Problems, opened by the 



following Paper: — 



The Afforestation of Water Catchment Areas. 

 By Professor Augustine Henry, M.A.^ 



The afforestation of water catchment areas is a hygienic measure as well as a 

 means of increasing the timber reserves of the nation. Many towns obtain their 

 water supply from catchment reservoirs constructed to impound the water falling 

 on upland and sparsely peopled tracts. Such gathering grounds in the Pennine 

 range supply most of the great centres of population in Lancashire, Yorkshire, 

 and Derbyshire. Other catchment areas are situated in Wales, Cornwall, and a 

 few other districts in England, and in many parts of Scotland. In many cases 

 the water authorities have only leased the water rights and have not acquired 

 the ownership of the gathering grounds. For the prevention of pollution of the 

 water, they have relied mainly on the 61st Section of the Waterworks Clauses 



' The subject of the afforestation of water catchment ai'eas in Great Britain 

 and Ireland is fully treated in chapters vii.-xii. of Fore.ifs, Woods, a»fi Trees 

 in relation to Hygknt, by Professor Aug. Henry, published in November, 1919. 

 These chapters are illustrated with sketch maps, plans, etc. 



