322 ASSIMILATION. 



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

 (C^H,jO|;) 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 b}- the following statement of 

 a theory widelj- taught. 



848. Formic aldehyde hypothesis. According to Gautier,^ 

 chlorophyll exists in two conditions, white chJorophyll, rich in 

 h^-drogen, and green cMorophyll^ poorer in this element. By his 

 h3-pothesis the yellow ra}- absorbed b}' the assimilating tissues 

 furnishes a certain amount of energ3- which is partiallj- con- 

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

 tion) ; and at the same time it permits the chlorophj-ll granule to 

 decompose the water with which the protoplasmic mass is satu- 

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



■-gives rise to formic acid (CHgO^), which in its turn is reduced to 

 formic (or methylie) aldelyde, CII^O. Tlie latter has the same 

 atomic proportions as glucose (C^Hj^Oy). 



849. Whether, in assimilation, the ternarj- 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 comijound. When this unsaturated 

 compound is oxidized,'^ a definite amount of energ}- of motion 

 is set free, and this is manifested to us under one of its many 

 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. Tlie energy of motion in solar 

 radiance is treasured for a time in the ternarj- 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.' Attention has 

 already been called to the interesting observations bj' this bota- 

 nist on the constitution of chlorophyll granules. In jjrosecuting 

 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 name hypochlorin. According to him, when 



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

 ^ Compare Claude Bernard, IjeQons sur les Plienomfcnes de la Vie, 1878. 

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



