o'2'2 ASSIMILATION. 



847. Glucose. It is held by some that this product is glucose 

 (C 6 H 12 O 6 ) or some substance having the same atomic propor- 

 tions of these elements. Early and not well-defined views in 

 regard to glucose may be replaced by the following statement of 

 a theory widely taught. 



/ / 



848. Formic aldehyde hypothesis. According to Gautier, 1 

 chlorophyll exists in two conditions, white chlorophyll, rich in 

 hydrogen, and green chlorophyll, poorer in this element. By his 

 hypothesis the yellow ray absorbed b}' the assimilating tissues 

 furnishes a certain amount of energy which is partially con- 

 verted into heat, and promotes evaporation of water ( transpira- 

 tion) ; and at the same time it permits the chlorophyll granule to 

 decompose the water with which the protoplasmic mass is satu- 

 rated. In the presence of CO., and H 2 O the reducing process 

 -gives rise to formic acid (CH 2 O 2 ), which in its turn is reduced to 

 formic (or methylic) aldehyde, CH 2 O. The latter has the same 

 atomic proportions as glucose (C 6 H 12 O 6 ). 



849. Whether, in assimilation, the ternary substance be for- 

 mic aldehyde, or glucose, or starch, it is certainly a substance 

 capable of undergoing further oxidation, and hence, chemically 

 speaking, an unsaturated compound. When this unsaturated 

 compound is oxidized,- a definite amount of energy of motion 

 is set free, and this is manifested to us under one of its man}' 

 phases, namely : (1) movements of the whole plant, as in some 

 of the lowest organisms ; (2) movements of liquids within the 

 plant, as in the transfer of matter to points of consumption ; 

 (3) heat; (4) electrical disturbances, and all the proper vital 

 activities correlated with these. The energy of motion in solar 

 radiance is treasured for a time in the ternaiy and derivative 

 products, thence to be released as occasion requires. 



850. It is proper to refer at this point to a novel view in 

 regard to the product of assimilation which has received much 

 adverse criticism ; namely, that of Pringsheim. 3 Attention has 

 alread}- been called to the interesting observations by this bota- 

 nist on the constitution of chlorophyll granules. In prosecuting 

 his investigations he became convinced that the peculiar colored 

 substance which is extruded from the granules under the influ- 

 ence of certain agents is a product of assimilation. To this 

 product he gave the mxmehypochlorin. According to him, when 



1 La Chimie des Plantes. Revue Scientifique, Feb. 10, 1877, p. 767. 



2 Compare Claude Bernard, Lecons sur les Phenomenes de la Vie, 1878. 



3 Jahrb., xii., 1879-1881, p. 288. 



