Imbibition and Growth in Fruits. 



165 



fying 45 on August 3. Great daily variations in size, with a net total 

 increase, were displayed every day. Usually enlargement could be 

 detected between noon and 2 o'clock, which continued until 8 or 10 

 the following morning. If the sun r©se clear, shrinkage began imme- 

 diately. If the morning was foggy it would be delayed. Minor vari- 

 ations might be brought about by the shade of clouds, especially notice- 

 able at noonday August 6 and to be seen at other times. 



12 p.m. 



I2p.m 



12 p.m. 



12p.m. 



12 p.m. m. 



Fig. 48. — Variations in volume of nut of Juglans during 56 days. Enlargement is denoted by 

 downward course of pen tracing, X 10. The lowermost section of the figure gives auxographic 

 record of swelling of a nut in a dark room on a branch 30 cm. in length with the cut end in a 

 vessel of water. Swelling for 20 hours occurred after shrinkage began as denoted by upward 

 course of pen tracing. 



After these facts were noted, experimental modifications were 

 arranged. Temperatures were taken from a branch 16 mm. in thick- 

 ness which were probably within a degree of that of the nut at all 

 times. A screen was arranged to cut off the direct rays of the sun at 

 midday, the nut being exposed for about 4 hours in the forenoon to di- 

 rect illumination. The temperatures ranged from 14° to 25° C. The 

 occurrence of fogs and of rain added to the variations in the conditions 

 affecting transpiration. The shrinkage in the forenoon was abrupt 

 and marked, being lessened on foggy days, and reaching an extreme of 

 4 mm. when the temperature rose from 14° to 25° C. in the 4 hours, 

 while it was on no day less than one-fourth this amount. The increase 

 varied from a minimum growth of less than 0.1 mm. on a cool, foggy 



