320 
Journal of Agricultural Research 
Vol. XI, No. 7 
Table I .—Amounts of hydrocyanic acid absorbed by the plants during fumigation 
[Results expressed as percentage of hydrocyanic acid in dry weight of plants] 
Set No. 
Time 
after fumi¬ 
gation. 
Percentage 
of hydro¬ 
cyanic acid 
to dry 
matter. 
Injury to plants. 
Dose. 
Set I. 
Hours. 
0 . O 
O. 0037 
.0047 
. 0041 
Slight burning. . . 
Severly injured. . 
.do. 
1 gm. of potassium cyanid 
per cubic meter for 1 hour 
Do. 
Do. 
Set II. 
. 0 
. 6 
.do. 
Do. 
1. 2 
.0037 
. 0027 
. 0100 
2. 0 
.do. 
Do. 
. 0 
.do. 
1 gm. of potassium cyanid 
per cubic meter for 1.5 hours. 
Do. 
Set III. 
i- 5 
5-6 
. 0 
.0077 
. 0032 
. 0006 
.do. 
.do. 
Not injured. 
1 gm. of potassium cyanid per 
cubic meter for 1 hour. 
Do. 
Set IV. 
1. 
. 0000 
.....do. 
Set V. 
. 0 
. 0090 
Severely injured.. 
1.25 gm. of potassium cyanid 
per cubic meter for 1 hour.. 
Do. 
2. 0 
. 0060 
.do. 
In the work reported in the previous paper (15) there was evidence 
that the absorbed hydrocyanic acid was given off from the leaves into 
the atmosphere after removal from the fumigation chamber, since 
plants were least injured when put under conditions favorable to rapid 
evaporation of the hydrogen cyanid. That the acid, howevet, may be 
partly or completely destroyed in the tissues is suggested by the work 
of Schmidt (18) and of Dezani (7), in which there was reported the 
destruction of a considerable portion of the absorbed or injected cyanid, 
by the sap of fruit, stem, and leaves. To determine, if possible, the 
fate in tomato plants of hydrocyanic acid absorbed during fumigation, 
resort was had to Mirande’s (13) sodium-picrate test paper for the de¬ 
tection of the acid given off by leaves. After fumigation one plant 
was placed in a bell jar just large enough to contain it, with a strip of 
the moist test paper suspended among the leaves from the top of the 
jar. The leaves from another plant were packed loosely in a jar with 
strips of test paper. After two hours a slight orange tinge was observed 
on the latter paper, but none on the paper under the bell jar. The 
color represented an amount of evolved cyanid gas equal to only an 
extremely small fraction of the amount that must have been contained 
in the leaves. It seems, therefore, that most of the hydrocyanic acid 
is destroyed by the tissues, being either united with sugars or converted 
into ammonia. It is rather probable that the hydrocyanic acid which 
actually gains entrance to the cells is never evolved from them again 
and that the acid which is still within the intercellular spaces and in 
the cuticle at the close of the fumigation may be evaporated into the 
atmosphere if placed under the proper conditions. 
