DEPARTMENT OF EXPERIMENTAL EVOLUTION. 143 



VEGETABLE SAPS; OSMOTIC CONCENTRATION. 



These studies, conducted primarily by Dr. Harris, have been out- 

 Uned in considerable detail in preceding Year Books. The time 

 available for these studies during the current year has been chiefly 

 devoted to field work, but a discussion of the osmotic concentration of 

 phanerogamic epiphytes, based on studies in Jamaica and in sub- 

 tropical Florida, has been published. In this it has been shown that 

 the concentration of the tissue fluids of epiphytic Bromeliacese, Pipera- 

 cese, and Gesneracese is far lower than that of terrestrial vegetation. 

 Furthermore, in the Bromeliacese, Orchidacese, and Piperacese the 

 concentration of the species of the Jamaican rain-forest is lower than 

 that of those found in the hainmocks of subtropical Florida- 

 Two periods have been devoted to work in the field. The first 

 covered the months of January, February, and March, which were 

 spent in the mainland swamps and on the Gulf Keys of the west coast 

 of Florida. The second covered the months of July and August, which 

 were devoted to work along the Atlantic seaboard from the mouth of 

 the Chesapeake to Biscayne Bay. These operations were carried out, 

 in cooperation with the Department of Botanical Research, on a 

 small yacht kindly placed at Dr. Harris's disposal by a friend. Mr. 

 John V. Lawrence and Mr. M. C. E. Hauke, of the University of 

 Chicago, took part in the operations along the Atlantic coast. Over 

 1,000 determinations of osmotic concentration were made by the 

 cryoscopic method in these two field operations, but the data are not 

 yet organized for discussion. 



COOPERATIVE WORK ON HUMAN NUTRITION. 



During the year Dr. Harris has published jointly with Dr. Francis 

 G. Benedict, Director of the Nutrition Laboratory of the Institution, 

 a "Biometric Study of Basal Metabolism in Man." This book is a 

 compendium of statistical information, not only for the student of 

 nutrition, but also for the anthropologist. With the assistance of his 

 biometric assistants, Mr. Harris has worked out numerous correlations 

 between age and stature, age and weight, weight and body-surface, 

 weight and pulse-rate, weight and heat production, and many other 

 elements involved in modern calorimetry. These correlations are 

 worked out for athletes, for men in general, for women, for infants, and 

 comparisons are made for diverse races. Some of the results of the 

 study are to demonstrate practically no relationship between basal or 

 normal pulse-rate and body-weight in adults, or between pulse-rate 

 and stature. The larger gaseous exchange is associated with a more 

 rapid pulse-rate, and the same is true of more rapid heat production. 

 There is a close relation between gaseous exchange and body-weight 

 and between total heat production and body-weight. It appears that 

 throughout the whole range of adult fife the heat production of in- 



