786 
Journal of Agricultural Research 
Vol. XXVII, No. io 
fluctuates during the day, they concluded that it is the first sugar formed 
in photosynthesis. Strakosch (17) studied the sugars in the leaves of the 
sugar beet by microchemical methods and concluded that dextrose is the 
first sugar formed in the mesophyll of the leaves of this plant. Parkin 
(u) from his observations on the carbohydrates of the leaves of the 
snowdrop {Galanthus nivalis) expressed the opinion that cane sugar is 
the first recognizable sugar to appear in the leaves of this plant and that 
the dextrose and laevulose rise from the inversion of cane sugar. He 
also found that there is more cane sugar in proportion to reducing sugars 
in the leaves during the earlier part of the growing season than during 
the latter part. Davis (j, 4, 5) and his coworkers concluded from their 
investigations of the carbohydrates of the leaves of the mangold and 
potato that cane sugar is the first sugar formed in the mesophyll of the 
leaves under the influence of chlorophyll and sunlight. They believed 
that this cane sugar is transformed into the hexoses in the veins and 
midribs of the leaves and that it is translocated to the places of storage 
in that form. They observed, as did Parkin, that in the earlier part of 
the season cane sugar is present in the leaf tissue in excess of the hexoses, 
but later in the season the reverse is true. Dixon and Mason (6) con¬ 
cluded from microchemical tests that hexoses are the first sugars formed 
in photosynthesis in the chloroplasts and that the comparatively large 
amount of cane sugar observed in chemical analyses is only a temporary 
storage product in the vacuoles of the green cells. Spoehr (16) in his 
observations on the seasonal variation of carbohydrates in Opuntia 
phaeacantha found that a low water content and high temperatures are as¬ 
sociated with an increase of polysaccharids, a decrease of monosac- 
charids, and an increase of pentosans, while a high water content and 
lower temperatures are associated with a decrease of polysaccharids, an 
increase of monosaccharids, and a decrease of pentosans. Colin and 
Belval (2) could detect no carbohydrates in the leaves of the wheat plant 
except cane sugar and its hydrolytic products. Ver Hulst, Peterson and 
Fred ( 18) found that the pentosans of the leaves of corn approximated 19 
per cent of the dry weight of the leaves from the time of tasseling to the 
dent stage, while the free pentoses amounted to only 0.52 per cent of the 
dry matter of the leaves during the same period. 
EXPERIMENTAL METHODS 
cultural methods 
The plants were grown under field conditions in rows 44 inches apart. 
The corn plants were thinned to a distance of 2 feet in the row and the 
sorghum plants to approximately 1 foot. The soil was kept free from 
weeds by hoeing, but no other cultivation was given. The moisture 
in the soil at the various periods of leaf sampling is given in Table I. 
collection oe material 
With but one exception, the experiments extended over a period of 24 
hours, and the material for chemical analysis was collected at two-hour 
intervals during that time. The three uppermost fully unfolded leaves 
of the plants furnished the material in each case. After the leaves had 
been stripped from the plants, the distal third and the basal third of each 
leaf were discarded and the remaining portions, after the midribs had 
