234 Transactions of the Royal Canadian Institute 



Min.: 60 60 60 

 Rate.: 45 95 47 



Jy. 16, beginning with 8 hr. reading. Sunlight (figure 10): 

 Min.: 60 48 12 25 10 16 leaves 9 uviol mirrors 



cut off low r.h. 10.03 



Rate: 23 19 -50 -12 60 o 9.51 67 



Min.: 20 40 4 r.h. raised 40 red 16 19 blue 16 normal 



to ca. sat. high high conditions 



Rate.: 105 8 o at 11.07 57 r-h. 130 63 r.h. 75 restored 

 Min.: 30 mirrors 45 chamber closed -uviol 



13.05 max. t. and illumination 



Rate.: 42 40 at 13.50 



Min.: 10 23 red 27 blue 10 12 normal 48 60 60 



conditions 

 Rate.: 18 83 100 120 100 restored 56 30 35 



15.12 

 Jy. 25, beginning with 8 hr. reading. Thin high fog: 

 Min.: 60 60 60 60 60 78 humidity 42 60 60 60 60 60 60 



raised at 

 Rate: 20-5 2 6 o 10 13.18 43 45 30 30 25 37 20 



Jy. 26, beginning with 8 hr. reading. Sunlight. Maximum t. 71: 

 Min. : 60 60 60 60 40 humidity raised 20 20 40 20 fog at 40 60 



at 11.40. Wilting i3-3o 



Rate: 10 5 0-5 15 in other plants. 00 15 15 67 45 



The raising of the vapour tension in this instance (July 26th) was 

 not followed by a very marked efTect. The absence of minus rates after 

 1 1 .40 means, however, that this part was no!, affected to the point of wilting, 

 which on the other hand was very evident in neighbouring plants. 

 With the advent of fog the rate rose. 



Ag. 12, beginning at 7 hr. Sun all day. Part inclosed all day in chamber with mirrors 

 and uviol glass. Hour periods. Humidity raised to ca saturation 14 hr. 

 Rate: 20 25 30 35 25 35 20 35 45 55 75 25 15 

 Temp.: 62 117 122 



The internode was shaded at 14.50 hour. The high temperatures 

 affording a rigorous condition were probably responsible for the lesser 

 total growth on August 12th, as compared with August nth (see fig. 8). 

 We note the exceptionally high rates from 8-12 hour which occurred 

 very seldom. 



EFFECT OF CHANGES IN ILLUMINATION 



The preceding data show that conditions (shade, high relative 

 humidity) which reduce evaporation from the plant, or which reduce 

 its transpiring surface, permit increased growth. The use of shade 

 however, reduced the light. It remained to determine what effect 



