20 
BULLETIN 57, HAWAII EXPERIMENT STATION 
Table 8. — Effect of copper sulphate upon germination and rotting of edible canna 
rootstocks 
Kind of seed 
Treatment 
Propor- 
tion of 
rot in 
germi- 
nated 
seed 
Number 
of seed 
germi- 
nated 
Number 
of stalks 
Appearance 
of stalks 
CuS04, 5 per cent for 15 minutes 
CuSO<, 5 per cent for 45 minutes 
CuSO<, 10 per cent for 15 minutes 
CuSCh, 10 per cent for 45 minutes 
H 
3 
2 
2 

3 
1 



3 
2 
1 

3 
9 
8 
7 

9 
2 



6 
4 
9 
7 

9 
Good. 
Poor. 
Fair. 
Control (no treatment) 

Attached spike 
CuS04, 5 per cent for 15 minutes 
CuS04, 5 per cent for 45 minutes.. .. 
Medium. 
CuS04, 10 per cent for 15 minutes 
CuS04, 10 per cent for 45 minutes 
Control (no treatment) 
H 
% 
H 
Immature rootstock, 
two buds. 
CuS04, 5 per cent for 15 minutes 
CUSO4, 5 per cent for 45 minutes 
CuS04, 10 per cent for 15 minutes 
CuS04, 10 per cent for 45 minutes 
Good. 
Fair. 
Poor. 
Control (no treatment) 
H 
Excellent. 
Copper sulphate did not prevent rotting of the seed. In fact, the 
treatment apparently increased the tendency to rot. Even the 
mildest treatment depressed germination. Of the three kinds of 
seed tested, the subsurface type was the most resistant both to the 
disinfectant and the rot. Partial rotting of the seed apparently 
had no effect on the vigor of the resulting plant, but where rot had 
penetrated to the portion of the seed adjoining the developing bud, 
there was a marked stunting of the stalks and a tendency toward 
profuse development of buds. Examination of the rotted seed 
showed somewhat darkened and watery tissue, nearly all of which 
was worm-infested. Although the worms feed mostly on decayed 
tissue they probably increased the rate of decay by opening fresh 
tissue. Rotting proceeded from the base of the seed where it had 
been attached to the parent, or along the side from which an off- 
spring had been removed. (Fig. 12.) 
Immersing lots of seed similar to those treated with copper sulphate 
in mercuric chloride in concentrations of 8 and 16 grams per gallon 
for periods of 15 and 45 minutes for each concentration did not have 
any toxic effect on germination or prevent rot. 
Although edible canna rootstocks remain dormant and in excellent 
condition when they are left undug in the ground for 12 months 
(20 months after planting), they deteriorate rapidly upon exposure 
after digging. One of the causes of deterioration after digging may 
be discovered by evacuating a rootstock under water. Bubbles 
will rise from all parts of the surface and the rootstock will increase 
8 to 10 per cent in weight. The moisture of freshly dug rootstocks 
evaporates rapidly through the epidermis, and the resulting influx 
of air opens the way for fermentation and decay. Since fermenta- 
tion and destruction of sugars take place in 15 to 21 days (9), pro- 
longed storage of the seed tends only to increase rot and to reduce 
vitality of the buds. 
Frequent observations have shown that the original seed of a hill 
18 months old is in excellent condition. At times rot appeared to 
have begun and to have partly destroyed the seed, while the remainder 
