308 The Physiology of Plants BOOK in 



sugars present, and their variations under different con- 

 ditions of formation and consumption. Brown and Morris 

 admitted that this result was not in accordance with their 

 expectations. They said, ' there seems every reason to 

 believe that this cane sugar, which may be regarded as the 

 starting-point of all the metabolic changes taking place in 

 the leaf, functions in the first place as a temporary reserve 

 material, and accumulates in the cell sap of the leaf 

 parenchyma when the processes of assimilation are 

 proceeding vigorously.' They attributed the glucose and 

 fructose to the hydrolysis of cane sugar, and held that 

 the maltose is the product of a process of digestion of 

 starch. 



Their view that cane sugar is the first sugar formed has 

 not been universally accepted. Their own suggestion that 

 it is certainly a temporary reserve product, though less 

 evidently so and less stable than the starch, makes it 

 possible to think that simpler sugars of the glucose 

 and levulose types may precede it in the formative pro- 

 cesses, being, however, very rapidly converted into cane 

 sugar as the quantity increases. 



At the end of the century the question still remained 

 an open one. 



In support of the hypothesis that formaldehyde is a stage 

 in the construction, we had very little direct evidence. 

 In 1888 Bokorny made a number of experiments with 

 Spirogyra, feeding the alga with formaldehyde in various 

 ways, to see if it could then form starch. He always 

 failed with the aldehyde itself, which proved poisonous, 

 but he succeeded with sodium oxymethyl sulphonate and 

 with methylal, both of which slowly give it off. His 

 experiments cannot be held to prove its normal occurrence, 

 for many other substances enable the plant to form starch. 

 At the end of the century Pollacci claimed to have shown 

 the presence of formaldehyde in green leaves, and in 1897 



