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I left Baltimore on October 13, 1905, for Jamaica, where I at 

 once took up my residence at the tropical station of the Garden, 

 at Cinchona, remaining until May. 



The general plan of my work was to make a study of the 

 physiological plant geography of the Blue Mountain region 

 above an altitude of 4,500 ft., and the various lines of investiga- 

 tion which this embodied were carried on more or less concur- 

 rently. I made a digest of the old meteorological records for 

 Cinchona, and other nearby points, in regard to air and soil tem- 

 terature, humidity and rainfall. With these climatic data as a 

 basis I then endeavored to determine the exact departure from 

 them of the conditions in a number of plant habitats varying in 

 topographic position, exposure and altitude. To this end I 

 secured weekly records with air and soil thermographs and with 

 a hygrograph, and also made observations as to the percentage 

 of cloudiness and fog, and took photometer readings of the in- 



the extreme constancy of the temperature, the height and con- 

 stancy of the humidity, the prevalence of cloud and fog, and 

 the large amount and frequency of rainfall. 



Selecting certain characteristic trees and herbaceous plants I 

 made a study of their rates of transpiration, using chiefly the 

 method of weighings and the potometer method. The daily 

 march of transpiration was determined by hourly readings, and 

 simultaneous readings were taken of temperature and humidity 

 and of evaporation as registered by a form of evaporimeter de- 

 vised by Dr. B. R. Livingston. After thus determining the con- 

 bined influence of natural conditions upon the daily cycle of 



influence in the same species of variations in heat, light and hu- 

 midity operating separately, but I was able to carry out this plan 

 only in part. The rates of transpiration showed a high degree 



under favoring conditions as to these factors and light some high 



were found to accompany cloudiness and high humidity, together 

 with the prevalence of these conditions, particularly on the 



