308 President's Address. 



tion. This carbon-assimilation is by all admitted as a fact, 

 and as in some way or other connected with the presence 

 of chlorophyll, but what is the relation, and what are the 

 first products formed in the assimilation, have been the 

 basis of numerous and conflicting hypotheses advanced. 

 That starch and oil and other substances in the corpuscles 

 are products of the carbon- assimilation is accepted — the 

 process by which they result, and how far the chlorophyll 

 is concerned, is the matter for discussion. There has also 

 been controversy as to the light-rays which bring about the 

 assimilation. Lommel advanced a purely physical hypo- 

 thesis, assuming that the rays most strongly absorbed and 

 of the greatest mechanical intensity, were efficacious. But 

 this has been quite disproved, and the rays most efficient 

 are the yellow and adjacent ones. 



The chemical assimilation hypothesis may be arranged 

 in three groups according to the part the chlorophyll is 

 supposed to play in the process: — (a) Those which assume 

 chlorophyll to be formed before assimilation, and to cause 

 it directly. To this we have subscribing Liebig, Bohm, 

 Sachs, Pfeffer, Risler, Horsford, Bayer, Erlenmeyer, and 

 others. (6) Chlorophyll is formed in the process of 

 assimilation, and is both a consequence and a cause of 

 it. The chief supporters of this hypothesis are Kraus, 

 Wiesner, and Timarjaseff. (c) Chlorophyll is formed in 

 assimilation, and is a consequence only. Meyer, Mulder, 

 and Morot, and recently Sachsse, have advanced this view. 

 The details of the process are regarded by those supporting 

 the same hypothesis by no means in the same way, and 

 the first assimilation product is difi'erent in the opinion of 

 the several observers. Thus Liebig supposed a gradual 

 deoxidation taking place, resulting in the primary formation 

 of organic acids. Eisler and Horsford attributed the process 

 to iron salts in the chlorophyll, the former maintaining that 

 iron protoxide becomes converted into peroxide ; the latter 

 regarding iron phosphate (of which Fremy's phylloxan thine, 

 one of his supposed constituents of chlorophyll, consists) 

 as the main agent by which the chlorophyll reduces the COg. 

 Bayer and Erlenmeyer assume a dissociation of the CO2 

 the former recognises a likeness between chlorophyll and 

 haemoglobin of the blood, in that it can fix carbonic 



