CARBOHYDRATE METABOLISM AND GROWTH IN EDIBLE (ANNA 33 
crop also should be ascertained by its specific gravity. A simple 
method consists in weighing a lot, say, 50 pounds, of cleansed root- 
stocks in a wire basket, first in air and then immersed in kerosene. 
The starch content can then be ascertained by referring to Table 5, 
page 11. 
SUMMARY 
In this series of experiments, made to study continuously the 
growth of edible canna {Carina edulis) and the occurrence of sugars 
and their changes during translocation and ultimate storage as starch 
in the plant, it was found that sucrose is the chief sugar of the leaves; 
the hexoses are present in only very small quantities, and the hexose- 
sucrose ratio is always very low. This is true of leaves from an old 
mature plant as well as from a young, rapidly growing plant. The 
percentage of sucrose is lower in the midribs and the sheaths than in 
the leaves, whereas that of the hexoses is much higher. In the stem 
proper the hexoses are present greatly in excess of^the sucrose. 
The sucrose in the apical part of the rootstock, as compared with the 
stem, increases and the hexoses correspondingly decrease. In the 
basal part of the rootstock both sugars usually decrease, especially 
the hexoses, which reach a very low percentage. The hexoses are 
therefore thought to be the chief sugars of translocation and the 
starch in the rootstocks to be formed from sucrose rather than from 
the hexoses. 
A study of plants of different stages of maturity shows that the 
quantity of hexoses is much less in the immature stems than in 
the mature stem, owing to the diversion of the flow in the former to 
the apical growth of the plant. This indicates the value of the 
mature stem in the synthesis of food material. The sucrose content 
of the rootstocks shows a similar variation to the hexoses of the stem, 
the immature rootstocks having a much lower percentage of sucrose 
than the mature ones. 
Young and vigorously growing rootstocks are characterized by a 
high percentage of the hexoses which occasionally exceed the sucrose. 
In the more mature rootstocks the hexoses are consistently low in 
quantity indicating their association with the growing parts of the 
rootstock. The concentrations of the hexoses in the stem and of 
sucrose in the rootstock would seem to be good indicators of the 
rate of transposition of sugars and their ultimate storage as starch 
in the rootstock. The sucrose of the stem and the hexoses of the 
rootstock are usually more constant and do not seem to correlate so 
well with growth, as determined by observations. 
The sucrose content of the rootstock, especially one that is imma- 
ture, is lowered when normal growth is halted for a protracted period. 
A return of favorable growing conditions often fails to cause any 
increase in the sucrose content. This fact, together with the low 
starch content of the rootstock, indicates a loss of amylogenic 
power. 
Copious irrigation of a field of stunted plants may result in an 
increase of sucrose in the rootstock, but the increase seems to be due 
to the process of "germination," or hydrolysis of the starch already 
stored in the rootstock to support secondary growth development. 
