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Transactions of the Royal Canadian Institute 



hour the course of transpiration followed in general that of evaporation, 

 the former increasing somewhat more rapidly. With the clearing of 

 the fog the evaporation increased during two hours to a three-fold rate, 

 the transpiration meanwhile attaining its maximum. The form of the 

 graph shows that after lo hour there was a gradual checking of transpira- 

 tion and a decided falling off after noon. At the 1 1 hour all the terminal 

 internodes on both plants were turgid, but, while they remained so in 

 the leafless plant, they showed complete wilting by the 13 hour in the 

 other. In this case, these two or three hours previous to 13 hour were 

 the period of growth cessation and shrinkage, recovery from which was 

 complete by 16 hour. Plants growing under their normal conditions 

 (but not where growth records were m.ade) showed wilting in similar 

 manner, with synchronous recovery. On days when sunshine obtained 

 the evaporation rate attained by 9 hour was equal to that of the 11 hour 

 on July 13th, under which circumstances the wilting would doubtless 

 have fallen earlier. It seems therefore obvious that the checking of 

 growth, culminating in shrinkage when the conditions are stringent 

 enough, is the result of net water loss by the plant (Livingston and 

 Brown, '12; Lloyd, '12a, '13) produced primarily by the evaporation 

 conditions. 



TABLE 4. 

 Transpiration, evaporation, etc. July 12th, 13th, 1912. 

 Cylindrical black porous cup, area 48 sq. cm. (fig. 6). Situation: a 

 steep eastern slope at Coastal Laboratory. 



Fog. Sun at 10 hr. Turgid. Wilting at 12. Shade (of trees) 15.20. Becoming 



turgid at 15 hr. 

 Evaporation for a fog day, Jy. 8 



I 0.0 Jo. 2 I 0.35I I.I I 1.45I 1-7 I 2.15! 1.6 I 1.15I 1.2 I 0.75! 0.6 



Total evaporation for a sunny day, July 13th, 22.65; for a foggy 

 day, July 8th, 12.25. 



