4 BULLETIN 907, U. S. DEPARTMENT OF AGRICULTURE. 
that the effect is observable to the naked eye. Burned signifies 
severe injury amounting to the partial or total discoloration of 
numerous leaves, as by heat. - Smged indicates slight burning, ee 
cially at the tips or edges of leaves. 
Varying degrees of daranse to the plants were ss as follows 
in all experiments: | 
0—Plants entirely unaffected externally. 
1—Some of the tenderest undeveloped leaves or tips of’ tender 
shoots at least slightly injured. 
2—Tenderest tips with undeveloped leaves severely injured; fully | 
crown tender leaves sometimes ey affected; mature 
leaves uninjured. 
3—Tender growth, including fully developed new leaves, destroyed; 
old leaves slightly affected. 
4—Mature leaves in large numbers severely burned. 
5—One-half to entire plant severely burned. : 
THE EFFECT ON PLANT INJURY OF TEMPERATURE, LIGHT, AND MOIS- 
TURE BEFORE FUMIGATION. 
The fumigation of growing plants is usually conducted without 
regard to their environment prior to the gas exposure, barring the 
factor moisture relative to which a divergence of opinion exists. The 
experimental evidence presented in this paper bearing on prefumiga- 
tion conditions draws attention not only to the influence of moisture 
but also to that of temperature and light. Data on the influence of 
these factors are brought out in experiments 1 to 9, inclusive, as well 
as in 11, 12, 14, 15, and 18, these latter experiments being discussed 
under the subject of eae influences. Certain of these 
experiments, namely, 1, 2, 12, 14, 15, and 18, are of special value 
by reason of the number of poe earn environments also in- 
cluded in each experiment. 
EXPERIMENT 1. 
Condition during fumigation, shade, 58°-60° F. 
Dosage, 13 ounces KCN. 
Date, March 18, 1915, 8.45-9.45 a. m. 
Plants in each test, 2; total, 30. 
Remarks: Plants somewhat hardened. 
Resuits. 
| Condition before fumigation. 
Condition after fumigation. Dark, Had ae, Sun, 
60 58° F 68° Fu 
Birk- G00 Fo2 = = hese) 1 3 
SLE, Dee o We ee oe | 1 3 
fark ph O25 ee } 24 } 24 5 
Shade 02h le 24] 2 Sa 
Rosi Poe 2 ae ee pees 36 $44 5 | 
Pages 
1 Plants in sunshine for 2 or 3 hours before fumigation. Maximum sun temperature for day, 77° F. 
