CARBOHYDRATE METABOLISM AND GROWTH IN EDIBLE CANNA 
9 
very different. The inclusion of a part of the stem or the removal 
of the apical part of the rootstoek would thus introduce serious 
error into the determination of the specific gravity of the rootstoek 
as a whole. 
SPECIFIC GRAVITY AND ITS RELATION TO STARCH CONTEXT OF ROOTSTOCK OF 
DIFFERENT AGES 
The method used to determine specific gravity has been described. 
Table 3 shows the variations in specific gravity of canna rootstocks 
grouped according to stage of maturity, generation, and age of hill. 
Table 3. — Specific gravity of canna rootstocks of different ages 
=, 
3 months old 
5 months old 1 7 l A months old 
9 months old 
22 months old 

o 
Genera- 
tion 
Specific 
gravity 
• Genera- 
tion 
Specific Genera- 
gravity tion 
Specific 
gravity 
Genera- 
tion 
Specific 
gravity 
Genera- 
tion' 
Specific 
gravity 
1 
/First 
\Second .. 
Third ... 
1.030 . 
1.088 
1.102 . 

1.080 
First. 
Secon'i ... 
1.034 
1.000 
First 
Second ... 
1.065 First 
1.032 Second .. 
Third... 
1. 073 
1.104 
1.039 
1.054 
2 
1.104 
Third 
.977 
Third 
1.030 Fourth .. 
Fourth .. 
Fifth .... 
Sixth 
Seventh . 
1.093 
1.073 . 
1.086 
1.061 . 
1.07C 
3a 
3b 
Fourth . 
.971 Fourth 
.990 Fifth.... 
1.032 
JXot genealogized. When the hill reaches this staga it is practically impossible to separate according to 
generations because of its size. 
A number of variations are evident in Table 3. Each hill, consid- 
ered as a whole, showed a gradual rise in specific gravity with advanc- 
ing age. Starting with the 3-months-old hill having an average 
specific gravity of less than ] , the specific gravity continued to rise to 
the ninth month; thence to the twenty-second it varied slightly. In 
the early growth of the hill the first generation had the highest specific 
gravity, each succeeding generation showing a decreasing value. From 
seven and one-half months the second or third generation had the 
highest value; thence the value continued to decrease. The specific 
gravity of Group 2 was highest throughout; that of Groups 3a and 3b 
decreased, whereas that of Group 1 was variable, but always less than 
in Group 2. The average specific gravity of the canna rootstoek is 
below that of the potato (16), and the range of variation is much 
greater, owing largely to the fact that young and immature rootstocks 
as well as mature ones are found in every hill of canna, regardless of 
its age. 
To ascertain the relationship between the specific gravity, deter- 
mined by the method outlined by Wiley (16, pp. 369-371), and the 
other constituents of the canna rootstoek, a series of analyses was 
made of hills of different ages and from different localities. Table 4 
shows the relationship of the specific gravity to the starch, dry mat- 
ter, and solids other than starch in the canna rootstoek. 
35973—27 2 
