224 
Ingvar Jorgensen and Walter Stiles. 
values in the same samples is suspicious, and the most likely 
explanation is that in some cases, at any rate, they are apparent 
maxima and minima, due to errors in sampling. This is especially 
so in the case of the maxima at 2 p.m., which appear owing to the 
minima at 4 p.m. Thus, if the minimum value found for hexoses in 
this case were increased hy 7%, the minimum on the hexose curve 
would disappear, and we have already cited the instance in which 
the hexose content of two samples collected under similar conditions 
differed by 6%. 
It seems reasonable to conclude from Davis, Daish and Sawyer’s 
figures that the hexose and sucrose in the leaf increase during the 
day and then gradually decrease during the night. The maximum 
in these sugars in the middle of the night, at 2 a.m., is extremely 
difficult to account for on any other ground than error in sampling, 
for the leaf manufactures no fresh material, and yet the total 
carbohydrate in the leaf (pentosan, sucrose, hexose and pentose) has 
increased from 19-53% to 22-13% of the total dry matter of the leaf 
according to Davis, Daish and Sawyer’s complete analysis. These 
authors suppose this increase is due to the breaking down of a 
water soluble gummy substance in the leaf into carbohydrates. 
The relative variations in sucrose content are similar to those 
in August, although the percentage of sucrose is more than twice 
as great. The total hexoses present is about the same amount by 
weight as sucrose, and is much more than is present earlier in the 
season. 
The pentose content varies little throughout the day; it appears 
to diminish somewhat during the night. 
The results obtained for the last stage of growth are similar to 
those obtained for the intermediate stage. They are shown 
graphically in Fig. 16. As before, the sugar content is greater 
during the day than during the night. In this case, hexoses and 
sucrose show two maxima during the night, at 7 or 9 p.m. and at 
3 a.m. As we have already indicated, the data furnished by the 
experiments of Davis, Daish and Sawyer are insufficient to enable 
us to judge whether such night maxima in sugar content actually 
exist in mangold leaves, or whether their appearance in the curves 
is simply due to a sampling error. 
The results obtained by Davis, Daish and Sawyer in regard to 
carbohydrates in the mangold leaf may be summarised as follows :— 
(i.) All the sugars in the leaf increase in quantity from the first 
to the final stage of growth. 
