124 Presidential Address 



The algebraic expression given on page 64 for the 

 amount of the change is not quite the usual orthodox 

 expression for it; but it is one which I have reason for 

 putting forward, and is not a misprint. 



Page 76 



The long-standing puzzle as to how vegetable sap is 

 raised against gravity from the ground to the tops of the 

 highest trees has been practically settled by recent workers, 

 notably by Professor H. H. Dixon of Trinity College, 

 Dublin, who has made a clear statement of the way in 

 which osmosis, or molecular diffusion through semi-per- 

 meable membranes, enables it to occur. 



Page 80 



Higher plants can only assimilate inorganic material 

 after it has been first incorporated into more lowly organ- 

 isms. Harsh treatment of a soil is found helpful to the 

 beneficent and manuring bacteria; for, being low in the 

 scale of existence, they are hardier and more resistant to 

 hostile influences than the still microscopic foes which feed 

 upon them. Wherefore treatment which slays the one 

 indirectly benefits the other. This explanation is not yet 

 proven, but the facts suggest it as likely. 



Page 80 



The larval stage of the mosquito is passed in water, and 

 the larvae cling to and perforate the surface in order to 

 breathe. If the surface is oiled the surface tension is 

 diminished, the surface does not support them, and they 

 keep on sinking till they drown. But not every puddle or 

 dribble of liquid can be oiled, and so breeding places can be 

 guarded against partly by drainage and partly by allowing 

 no unperf orated vessel to remain as a trap for accumulated 

 water. 



