DEPARTMENT OF BOTANICAL RESEARCH.' 



D. T. MacDougal, Director. 



The attention of the staff and collaborators has been directed to the 

 study of fundamental problems in growth and hydration, carbo- 

 hj'drate metabohsm and nutrition, soil-aeration effects, using some of 

 the rarer inert gases, such as hehum and argon, and to the special 

 problems of physiology and ecology presented by the vegetation of 

 arid regions. Detailed descriptions of the results obtained are given 

 in the followmg paragraphs. 



GROWTH AND HYDRATION. 



Course of Growth in Trees as measured by the Dendrograph, hy D. T. 



MacDougal. 



The study and use of the dendrograph, which was designed in 1918 

 for the continuous recording of variations in tree trunks, have led to 

 the improvement of this instrument to its approximate final form. 

 Steps are being taken to render it available to other workers besides 

 the designer and his associates. Eighteen instruments, including 

 some differences in construction, have been operated by the designer 

 and his collaborators as noted below, and this cooperation has yielded 

 some valuable suggestions as to operation and improvement of the 

 apparatus. 



A weather-proof recorder and a new lever set have been tested and 

 adopted. 



The operations for the season of 1920 have included measurement 

 of 13 species of trees by observers as given below: 



Acer saccharum Marsh: New York Botanical Garden; by Dr. A. B. Stout. 



Platanus occidentalis L. and Populxis deltoides Marsh: Missouri Botanical Garden; by 

 Professor B. M. Duggar and Mr. F. S. Walpert. 



Pseudotsuga mucronata (Rafinesque) Sudworth and Pinus ponderosa Dougl.: Alpine Labo- 

 ratory, Pikes Peak, Colorado; by Dr. F. E. Clements and Mr. Gorm Loftfield. 



Picea pungens Engelm: Cottonwood Nursery, Wasatch Mountains, Utah; by Mr. C. F. 

 Korstian. 



Pinus scopulorum (Engelm.) Lemmon: Fort Valle}' Experiment Station, Flagstaff, Arizona; 

 by Mr. G. A. Pearson. 



Populus macdougalii Rose: Continental, Arizona; by Dr. W. B. McCallum. 



Fraxinus arizonica and Parkinsonia microphylla: Tucson, Arizona; by Dr. H. W. Fenner 

 and Mr. B. R. Bovee. 



Citrus aurantica: Citrus Experiment Station, Riverside, California; by Professor H. S. Reed. 



Qiiercus agrifolia Nee: two trees, Carmel, California; b}^ D. T. MacDougal. 



Piniis radiata Don.: four trees, Carmel, California; by D. T. MacDougal. 



In addition to the 13 species which have been measured during the 

 present season, a single season's records of Fagus grandifolia and of 

 Pinus chihuahuana were secured in 1919. The reduction of these rec- 

 ords is now under way and a technical treatment of the information ob- 

 tained will probably he ready before the opening of the season in 1921. 



1 Situated at Tucson, Arizona, and Carmel, California. 



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