426 
Journal of Agricultural Research 
Vol. XI, No. 9 
2. PLANTS WITH ROOTS IMMERSED IN AQUEOUS SOLUTIONS OF HYDROCYANIC-ACID 
GAS 
Turnip and lettuce seedlings and three months* old turnip plants were 
removed from the soil in which grown and the roots were immersed in 
hydrocyanic-acid gas solutions and sealed in as above. In this experi¬ 
ment, as in the former, all the plants were killed down to and including 
dilution 1.1742 gm. of sodium cyanid per liter (equivalent to 0.3522 per 
cent of hydrocyanic-acid gas over the solution). The minimum point 
at which the plants were normal was very close to the first series; but 
there was this difference: In three dilutions, 0.0091 to 0.00225 gm. of 
sodium cyanid per liter (equivalent to 0.00273 to 0.000675 per cent of 
hydrocyanic-acid gas over the solutions) an acceleration in growth was 
noticed, while none was noted in the first series. 
3. CUTTINGS IN AQUEOUS SOLUTION OF HYDROCYANIC-ACID GAS 
The various solutions of hydrocyanic-acid gas were made up as before, 
and cuttings of chrysanthemum (Chrysanthemum sp.) and wandering 
jew (Zebrina pendula) were partially immersed in the solutions. The 
plants in this series were the most resistant of any of those tried. From 
Table IV it will be seen that only in solutions containing 9.394 gm. of 
sodium cyanid per liter (equivalent to 2.818 per cent of hydrocyanic-acid 
gas over the solution) were all of the cuttings killed, the point of normality 
being 0.0733 gm. of sodium cyanid per liter (equivalent to 0.0219 per cent 
of hydrocyanic acid gas over the solution). 
The experiments on plants thus far have been with aqueous solutions 
of hydrocyanic-acid gas, in which some part of the plant was immersed. 
To make these experiments comparable with those on insects where the 
gas was used (instead of an aqueous solution of hydrocyanic-acid gas), 
it must be known whether or not the effect of hydrocyanic-acid gas on 
the leaves is comparable to the action of the gas solution on the roots. 
4. PLANTS WITH LEAVES EXPOSED TO HYDROCYANIC-ACID GAS, WITH ROOTS PROTECTED 
The ordinary-sized tumbler was partially filled with water, and inside 
the tumbler a whisky glass was placed containing y 2 ounce of hydrocyanic- 
acid gas solution, the first one having 9.394 gm. of sodium cyanid per 
liter (equivalent to 2.818 per cent of hydrocyanic-acid gas over the solu¬ 
tion) and being reduced one-half in each succeeding culture, as in previous 
experiments. Small seedling turnips were placed between the walls 
of the two glasses, with the roots extending into the pure water. Melted 
paraffin was then poured on the surface of the water, thus sealing in the 
plants and preventing the roots from coming in contact with the gas. 
By comparing the results with those of plants in aqueous solutions of 
hydrocyanic-acid gas it will be seen that the action was similar. With 
the gas acting only upon the leaves, all were killed, up to and including 
