PllESIDENTIAL xVDDRESS SECTION C. 



58 



iBaiiy of the physiological problems suggested by agricultural 

 practice and its difficulties. A plant physiologist is a botanist 

 as well as something of a chemist and a physicist. He needs the 

 co-operation of the chemist and the physicist, but his special 

 equipment enables him to co-operate with them in return, 

 bringing an experience of the research methods appropriate to 

 the study of plant functions and an intimate knowledge of the 

 plants themselves. 



This is reahsed in Europe and America. In the United 

 -States especially, representatives of various branches of plant phy- 

 :siology are attached to the staffs of the Agricultural Experiment 

 Stations and much valuable work has been accompUshed by 

 them. 



There are various physiological subjects of obvious practical 

 :application to which I might have asked your attention on this 

 occasion. I feel, however, that I could hardly do justice to them 

 in relation to the special problem's of this country, because my 

 residence here has not been long enough, and in Cape Town I 

 have not had opportunities of obtaining a fii-st hand acquaint- 

 ance with agricultural conditions and practice. The subject I 

 have chosen is, however, one which ranks second to none in 

 fundamental importance. 



The assimilation of carbon dioxide by the green plant is a 

 process on which depends the whole of the food supply of the 

 plant and animal worlds. It underlies the food supply of the 

 human race. The accumulations of carbonaceous matter by 

 plants of past geological epochs supply, moreover, in the form 

 of coal, the source of power for the bulk of our manufacturing 

 processes. Much has been heard recently of the possibilities of 

 alcohol as a source of power. This alcohol is also ultimately 

 derived from the products of the photosynthetic activity of the 

 green plant, and, like coal, represents a store of potential energy 

 obtained from the radiant energy of sunlight. This process well 

 merits the title of " cosmic function," which was first, I believe, 

 conferred upon it by T'imiriazeff, that distinguished Eussian plant 

 physiologist of whose death this year we have learned with regret. 



Touring the last twenty or thirty years our knowledge of this 

 function has been notably enlarged. Two names are chiefly 

 associated with the progress that has been made, those of F. F. 

 Blaekman of Cambridge, and Willstatter of Berlin. Much of the 

 work of Blaekman and his school is already well known. That 

 of Willstatter and his collaboratoi's is more recent and, partly 

 owing to the War, is less familiar to botanists than its importance 

 demands. 



Blackman's great achievement has been the successful 

 analysis of the influence of external conditions on the rate of 

 assimilation, which has laid the foundation for a deeper know- 

 ledge of the process itself. Willstatter has established on n firm 

 basis our knowledge of the pigments of the green chloroplast and 

 given us a further glimpse into the internal mechanism of the 

 process. The work of both has applications which extend bevond 



