2 3 ° Ingvar Jorgensen and Waller Stiles. 
sucrose is a later formed product, and he supports this conclusion 
with an analysis of leaf extract which shows only a negligible 
quantity of sucrose in the leaf (about one-sixth of the quantity of 
glucose) while the veins contain nearly five times as much sucrose 
as hexoses. Strakosch’s results are in direct contradiction to those 
of the English workers, whose work we have summarised in the 
preceding section of this chapter. Davis, Daish and Sawyer point 
out that Grafe’s test (1905) for fructose, used by Strakosch, is of 
doubtful applicability in presence of glucose, while the method used 
to localise glucose and sucrose, which is due to Senft (1904), is, 
according to Mangham (1915), untrustworthy when sucrose is 
present together with its hexose constituents. Davis, Daish and 
Sawyer criticise Strakosch’s results as well as Maugham’s identifi¬ 
cation of maltose in plant tissues, on the general ground that little 
reliance can be placed on such microchemical tests as a means of 
identifying one sugar in presence of others in plant tissues. The 
fact that Mangham should claim to distinguish between ^/-glucose 
and ^-fructose in the plant by means of the osazone test, when their 
phenyl osazones are of course identical, is not very reassuring as to 
the degree of reliability of his results. 
Such qualitative observations as those of Strakosch and of 
Dixon and Mason (1916) in any case cannot have the value of the 
quantitative researches recorded in detail in the preceding section 
of this chapter, and we find in all detailed quantitative examinations 
made of the carbohydrates of the leaf, that cane sugar is always 
present in the leaf in considerable quantity. We have already 
pointed out that all the workers who have obtained quantitative 
data have expressed the opinion that sucrose is the first sugar formed 
in assimilation, and that this is inverted into hexoses for translocation. 
When carbohydrate accumulates in the leaf in consequence of 
assimilation taking place at a greater rate than translocation, the 
excess of sucrose is supposed to be transformed into starch in 
Tropceolmn (Brown and Morris). In the potato, which also forms 
starch in the leaf, Davis and Sawyer (1916) appear to regard the 
starch as formed from hexoses, soluble starch, which appears in 
appreciable quantity in the leaf at the period when starch content is 
at a maximum, being an intermediate product. This view is based 
on the intimate relation between the content of hexoses and starch in 
the leaf throughout the day, a relation, however, which is not very 
obvious from Davis and Sawyer’s published curves (cf. Fig. 17). 
It must be admitted that the evidence in favour of the production of 
