104 GRKKXIIOfSI': FIM ICATIOX 



temperature, however, is accompanied hy a decrease in the rchui\e 

 htimidity. thus producing a tendency in the plant tt) close its 

 stomata. Ftu'ther during nigiit fttmigation, as has been shown, 

 the hydrocyanic acid enters primarily tlirotigh the ctiticle, and the 

 rate of diffusit)n will not l)e of as great importance as the nature 

 of the cuticle. Although most investigators consider that a high 

 temperature fa\ors injury. Tower states, "The results in \ariation 

 of temperature of the house during fumigation were l)v no means 

 as noticeable as had been anticipated ; indeed, as a result of these 

 tests, it would seem to make little difference whether treatment 

 should I)e gi\en in a warm or a cool house." (8). 



Throughout our experiments we found that a high. temi)era- 

 ture was benehcial rather than injtiriotis. Two ex])eriments may 

 1h' noted. ( ieraniimis, sweet peas, crimson. raml)ler rose, and cu- 

 cuml)ers were exposed for fotir hours to a dose of 7 oiuices per 

 1.000 cul)ic feet, at a temperature of 96° F. and a relati\e humidity 

 of 39%. The restilt was a btirning of the tips of the sweet peas, 

 the buds of the rose, a few of the \oungest leaves of the geraniums 

 and the shoots of the cucumbers. In the experiment previously 

 cited under relatixe humidity the tomatoes of Set I fumigated tuider 

 an average tem])erature of 48.5° F. were severely injured. Sets 

 in, I\^ and \\ 83.5° F. to 89° F., were either not injured or but 

 slightl}' injured. Figtire 26. A high temperature reduces the relative 

 humidity and increases evaporation, hence would act as a low rela- 

 tive humidit}' and would be benehcial. 



If the tem])erature is high during a short fumigation in airing 

 otit the cold air tends to deposit moisture upon the leaves of the 

 plants. This moisture contains hydrocyanic acid and in the case 

 (jf plants w ith thin cuticles will cause injurv. ( )ne stich case noted 

 in the work may be of interest. A greenhouse filled with letttice 

 was fumigated at the rate of Vi oz. of potassium cyanide to each 

 1,000 cu. ft., for a period of Ijj hrs. ddie temperature of the house 

 preceding ftmiigation was 50° F., but was raised to 58° F. before 

 the charge was put in. The relative humidity was 89%. In airing 

 out the house the temperature was lowered to 50° and remained 

 at that temperature for the rest of the night. The plants were 

 injured apparently' from the moisttire deposited upon them when 

 the house was aired. To pro\ e this ])oint lettuces were raised 

 imder similar conditions the following year and fumigated over 

 night with ;/> oz. of potassium cyanide per 1,000 cu. ft. without 

 injury to the ])hints. Later they were again fumigated in an attem])t 

 to reproduce the conditions of the preceding experiment. The 



