Nov. i2 ,1917 
Greenhouse Fumigation with Hydrocyanic Acid 
323 
The permanency of this recovery is shown by the following experiments. 
A uniform group of tomato plants about 17 cm. high was divided into 
four sets of 30 plants each. No. 6 was normal, unfumigated. No. 7 was 
fumigated from 7.20 to 8.50 p. m. with 1 gm. of potassium cyanid per 
cubic meter of air at a temperature of 13 0 C. Owing to the low tempera¬ 
ture half the plants were killed, and experimental work could not be 
started on the other half until four weeks later. No. 8 was fumigated 
with 0.25 gm. of potassium cyanid per cubic meter overnight 3 times at 
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Fig. 3.—Curves showing the hourly activity of the oxidases of fumigated and of normal tomato plants. 
2- week intervals. There was no visible injury. No. 9 was fumigated 
with 0.25 gm. of potassium cyanid per cubic meter overnight 10 times at 
3- day intervals. Samples for oxidase analysis were taken at intervals 
and prepared in the powder form. Figure 4 gives the results. The curves 
indicate that there is in general no permanent decrease in oxidase activity 
except in the group very frequently fumigated. 
Many other determinations on the fresh juice of tomatoes, working with 
both hydroquinone and pyrocatechol, confirmed the above results. 
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Fig. 4.—Curves showing the oxidase activity of fumigated and of unfumigated tomato plants over a period 
of eight weeks. F, close of fumigation. 
Catalase.—F or the quantitative determination of catalase activity 
0.025 £ m - °f the powder, or 0.13 c. c. of juice, was allowed to act on 2.0 
c. c. of 3 per cent hydrogen peroxid in Bunzel tubes graduated to read 
positive pressures (2). A temperature of 37 0 C. was always used, and the 
reaction allowed to continue for 15 minutes. According to Appleman, 
catalases are rapidly destroyed by contact with acid plant juices, and 
calcium carbonate has to be added as a preventive. This was not found 
to be the case with tomato juices, however, and calcium carbonate was 
not used in these determinations. 
