Dec. a?. 1915 Carbohydrate Transformations in Sweet Potatoes 
545 
to compare the changes in the roots during the period immediately after 
they were dug with those during a subsequent period of the same length. 
The second series of experiments was in all respects like the first except 
that the potatoes were dug on October 16 and placed in the experimental 
chambers on October 17 and 18. The length of time of storage was 12 
days. 
It was the object of the third series of experiments to determine the 
effect of removal of the vines on the initial carbohydrate changes in the 
sweet potato. The potatoes used in this series were, therefore, not dug 
until some time after the vines had been killed. The first frost, which 
killed the leaves but not the vines, occurred on October 22; a few days 
later, October 27, the vines were cut off close to the ground, so that from 
this time there would be no further transfer of materials from the vines to 
the roots. The potatoes were dug on November 6 and were thereafter 
treated as described for the other experiments, with the exception that 
the storage period was 10 days. 
methods op analysis 
The methods of analysis were essentially the same as formerly de¬ 
scribed. 1 Only a few exceptions need be noted. The samples for moisture 
determinations were covered with 95 per cent alcohol as before, but the 
alcohol was evaporated in a drying oven at 50° C. Thereupon the samples 
were dried to their lowest weight in a vacuum oven in a slow current of air. 
This procedure gave clean, nearly white samples. For the starch deter¬ 
minations 10 gm. were weighed out and the whole sample, instead of 
an aliquot, was extracted, ground, and used for hydrolysis. The sugar 
samples were put into flasks, which were then nearly filled with 70 per 
cent alcohol, with the addition of a little calcium carbonate, and boiled 
for a minute or two. The starch samples were stored, without boiling, 
in 95 per cent alcohol. 
GENERAL OBSERVATIONS ON THE EXPERIMENTS 
In the experiments described halves of the same sweet potato were 
compared with each other, the one being analyzed immediately and the 
other at the end of a 10 to 12 day period of storage. Two questions 
immediately arise regarding this procedure, which was adopted because 
different sweet potatoes of the same variety differ much in composition: 
First, are the halves of the same potato alike in composition; and, second, 
do the cut potatoes behave in the same manner as whole potatoes in 
storage ? 
Miiller-Thurgau 2 3 in his work on the common Iristi potato found tha t 
there were only slight differences in the sugar content of the two halv es 
1 Hasselbrmg, Heinrich, and Hawkins, L. A. Physiological changes in sweet potatoes during storage. 
In Jour. Agr. Research, v. 3, no. 4, p. 331-342. 1915* Literature cited, p. 341-342. 
3 Muller, Hermann, Thurgau. Ueber Zuckeranhaufung in Pflanzentheilen in Folge niederer Tempera- 
tur. Ein Beitrag zur Kenntniss des Stoffwechsels der Pflanzen. In Landw. Jahrb., Bd. n, p. 751-828. 
pi. 26. 1882. 
