President's Address. 309 



oxide, and sunlight then reaching the CO, a dissociation 

 takes place, oxygen is given off, and the CO remains fixed 

 with the chlorophyll, and then the simple reduction of CO 

 to formic aldehyde takes place, and this last is the primary 

 assimilation product ; the former holds that formic acid 

 and hydrogen peroxide result, and tlien subsequently the 

 formic acid is broken up and methyl aldehyde ultimately 

 formed. Bohm, Sachs, and Pfeffer regard the action as 

 catalytic, the details of the process being unknown, and 

 assume that starch is the primary assimilation product. 

 Of those who take chlorophyll to be a consequence 

 as well as a cause of assimilation, Timarjaseff assumes 

 a dissociation of the CO.,, and the CO combines with 

 one of the elements of chlorophyll which has been de- 

 composed by the light, and more chlorophyll is formed. 

 Kraus assumes a substance, leucophyll, which with chloro- 

 phyll exists in a plant ; the latter results from the former 

 by its combination with the product of a reduction of CO2. 

 This reduction is effected by leucophyll in light, and 

 the combination takes place by a predisposing affinity. 

 Wiesner assumes that as in liglit and air a chorophyll 

 solution is oxidised, the like must go on in the plant, with 

 this difference, that no free oxygen but the oxygen from the 

 CO., is used for oxidation of the chlorophyll, and the 

 chlorophyll is thus the reducing element of the COo, a 

 carbohydrate being ultimately formed. Sachsse revives an 

 old hypothesis of Meyer, Mulder, and Morot. Cliloro- 

 phyll is, he says, one of the first assimilation products, and 

 the mother substance of starch, and, on the other hand, 

 starch may be converted into chlorophyll. The xantho- 

 phyll element is first formed, and thereafter, with the 

 taking up of nitrogen, the true green matter is formed. 



From amongst these conflicting theories, and the irre- 

 concilable statements made in their support, it is difiicult 

 to form a satisfactory opinion as the true process of 

 assimilation. By chemists especially, however, the influ- 

 ence of the protoplasm in the decomposing and synthetic 

 processes has been practically ignored. Sachs and Pfeffer 

 recognise that it is a factor to be considered, and Borodin's 

 investigations upon asparagin show the important relation 

 between carboliydrate and nitrogenous-compound formation. 



