326 
Journal of Agricultural Research 
Vol. XI, No. 7 
excess of the normal. With greater injury (the two lower curves), 
however, the respiration is above normal even at the close of the fumiga¬ 
tion. It remained above normal throughout the experiments, periods of 
five to seven days. A normal fumigation with hydrocyanic acid there¬ 
fore results in a temporary decrease, followed by an increase in respira¬ 
tion. It is interesting to note at this point the correlation in the form of 
the curves of the catalase and respiratory activities, results similar to 
those found by Appleman in potato tubers. The curves of the oxidase 
activities, however, do not conform to either of these. Our results seem 
to confirm Appleman’s, that catalase is more significant in respiration 
than are oxidases. 
EFFECT ON PHOTOSYNTHETIC ACTIVITY 
Inasmuch as the photosynthetic activity of a plant may be checked 
temporarily or permanently by heat, asphyxiation, or anesthetics (8, 9), 
and as hydrocyanic acid influences the respiration of the plant, it was 
naturally concluded that the cyanid might affect photosynthesis. With 
a view to ascertaining this point, the appearance and disappearance of 
starch in tobacco (Nicotiana tabacum) and geranium (Pelargonium spp.) 
was followed. The test for starch was made by steeping leaves in boiling 
water for a moment, then immersing in warm alcohol to extract the 
chlorophyll, after which they were placed in weak iodin solution. The 
plants to be tested were placed in the dark for 24 hours, or until a starch 
test on the leaves was negative. When free from starch, the plants were 
divided into two sets, one of which was fumigated in a tight box in the 
dark; the normal set was also kept in the dark during the fumigation. 
The dose was 1 gin. of potassium cyanid per cubic meter, for one hour 
in the case of the tobacco, and for one and a quarter hours in the case of 
the geranium. At the close of the fumigation both sets were brought 
into the light. A strong starch test was obtained in the normal plants 
within an hour, but the fumigated tobacco required 5.5 hours, and the 
geranium 5 hours before even a slight starch test was obtained. By even¬ 
ing the starch content was still much less in the fumigated than in the 
normal. Frequent tests showed that it required about three days for the 
fumigated plants to recover normal activity. Similar tests were made 
with potatoes, cucumbers, and tomatoes, with like results. It is note¬ 
worthy that the first evidence of recovered photosynthetic activity cor¬ 
responds in general to the periods of recovery of the catalase and the 
respiratory activities. 
EFFECT ON TRANSLOCATION OF FOOD MATERIALS 
It was observed in the above experiments that the fumigated plants 
were not able to use up during the night even the small amount of starch 
that had been formed up to the previous evening. Evidently the trans- 
