236 THE PLANT. X. 



solutions of sugar were able to produce starch. From levulose 

 (10% solution) almost all the leaves tried produced starch,, a 

 smaller proportion were able to utilise dextrose, while still 

 fewer could form starch from galactose. Baeyer in 1870 

 suggested that the formation of carbohydrates by leaves was 

 probably effected by the formation of formaldehyde, O~CH 2 , 

 and its subsequent polymerization. Very little evidence in 

 favour of this view was forthcoming, however ; indeed Bokorny 

 in 1888" showed that formaldehyde itself would not act as a 

 source of starch owing to its poisonous action. In 18911 he 

 succeeded in using as a nutrient a dilute solution of sodium 

 oxymethylsulphonate, CH 2 (OH).S0 8 Na, which readily splits up 

 into formaldehyde and sodium hydrogen sulphite 



CH 2 (OH).S0 3 Na = OCH, + NaHSO a . 



By the addition of sodium or potassium phosphate the inju- 

 rious effect of the acid sulphite upon the plant could be 

 prevented, and he then found that the leaves of Spirogyrd 

 majuscula were able to form starch from a very dilute solu- 

 tion of this formaldehyde derivative. Baeyer's hypothesis was 

 thus confirmed. 



According to Brown and Morris]: cane sugar is probably the 

 first sugar formed in the process of assimilation. Its forma- 

 tion proceeds until the cell-sap attains a certain concentration, 

 varying in different plants, when starch granules begin to form 

 from it. These are intended as reserve materials and become 

 attacked by the diastase, present in all leaves, as soon as the 

 sugar solution, by diffusion to other portions of the plant, sinks 

 below a certain concentration. They think that inversion of 

 the cane sugar into dextrose and levulose precedes its trans- 

 location from cell to cell and that maltose is the chief product 

 of the diastatic action on starch ; that of the invert sugar 

 formed in the plant the dextrose is first used up in respiration 

 and tissue formation, and consequently that levulose enters 

 the stem of the plant in larger quantities than dextrose. 



The formation of carbohydrates, though perhaps the most 

 important function of the leaves, is by no means their only 

 one. 



* Landwirt. Versuchs-Stat. 1880. 



t Ber. deut. hot. Geaell. 1891, 103. ; J.C.S 1801, abst. 1589. 

 I Jour. Chem. Soc. 1893, Trans. 604. 



