E VERGEBEN TREES IN WINTER. 319 



cause an error in reading the water column. To prevent a violent 

 change of the temperature of the water in the tube, the whole 

 apparatus was immersed in a glass vessel filled with water, and 

 the experiments were always commenced after a lapse of time 

 sufficient to equalize the temperature both inside and outside the 

 tube. By this means, I equated the temperature in the glass 

 vessel and in the tube. The details obtained by this method 

 will be given in the description of each special experiment. 



The amount of transpiration was reduced, for the sake of 

 comparison with different kinds of plants, to the area of leaves 

 in n dm., and also to their fresh weight and dry weight in 100 

 grams. For measuring the area of leaves, I employed the 

 usual method of weighing pieces of paper cut in the same forms 

 as the leaves, the weight of the unit area being previously 

 ascertained. 



III. The Climate of Middle Japan. 



Before describing the details of my experiments, it will be 

 worth while to give a brief account of the climate of middle 

 Japan (Hondo) in which my observations were made. Since the 

 climate of this island is greatly influenced by the ocean, it has 

 a wide range and is rather inequable ; as a whole it is mild and 

 highly favourable to a luxuriance of vegetation. 



Temperature. The mean temperatures during the winter in 

 Tokyo'^ are 5.1°C. in December, 2.7°C. in January and 3.5°C. 

 in February ; the average temperature being, therefore, 3.8°C. 

 In January, the maximum is 15°C.; while the minimum is -6.5°C. 



1) Calendar for 1899 published by the Imperial University of Tokyo. 



