14 
BULLETIN 56, HAWAII EXPERIMENT STATION 
remains practically constant. Although the mangel is not a starch- 
storing crop, starch is found in its leaves in the early stages of 
growth, and disappears permanently as soon as the root begins to 
develop. 
In studying the variations in the carbohydrates of the leaves of the 
potato plant during a 24-hour period, Davis and Sawyer (5) observed 
that the sucrose in the leaves reaches its maximum at 2 p. m. 
Subsequent decrease is accompanied by an increase in the hexoses 
and the appearance of soluble starch in the leaves, indicating a 
change of sucrose into invert sugar and subsequent condensation into 
starch. The starch decreases during the afternoon and early part of 
the night, reaching a 
very low value between 
midnight and 2 a. m., 
apparently being con- 
verted into hexoses. 
Miller (11), working 
with the leaves of corn 
and sorghum, noted that 
the nonreducing sugars 
increase during the day 
and decrease during the 
night; whereas, the vari- 
ations in the reducing 
sugars are comparatively 
small and very irregular. 
The insoluble carbohy- 
drates, reaching a maxi- 
mum later in the day 
than the sugars, decrease 
rapidly after midnight. 
VARIATIONS IN DIFFERENT 
PARTS OF THE PLANT 
Analyses were made 
to determine the nature 
of the carbohydrates 
formed by photosyn- 
thesis in the leaf of the 
canna plant, and any 
change taking place during transposition through the stem to their 
final deposition as starch in the rootstock. The sap was extracted 
from a fresh part of each sample 6 and the sugars were determined as 
outlined under " Laboratory Methods," p. 6. The remainder of some 
of the samples was dried and ground, and the percentage of moisture 
and starch was determined. Table 6 gives the results of the analyses. 
Fig. 10.— Method of development of buds. Longitudinal section 
of a portion of a young surface rootstock. The bud develops 
at the base of the scale. The vascular bundles supporting its 
growth are to be seen extending far into the iuterior. Under 
normal conditions, B and C develop as vigorous primary growth, 
whereas A either fails to develop or appears as secondary growth 
at a later period, when it is known as a "top bud" 
6 These and subsequent samples for sugar determination were dug between 9 and 12 a. m. While the 
time of sampling has a decided effect on the sugar content of the leaves of a plant, the stems and roots are 
much less subject to daily variation. The results obtained would hardly be materially affected by the 
time of taking the sample in the case of the stem and rootstock. 
