DEPARTMENT OF BOTANICAL RESEARCH.^ 



D. T. MacDougal, Director. 



The fundamental features of growth, nutrition, and metaboUsm, 

 especially of the carbohydrates, soil aeration, and the problems of 

 physiology and phytogeography of plants of arid regions continue to 

 claim the major part of the attention of the investigative members of 

 the staff. The results of the activities of the year on subjects wdthin 

 the implied range are detailed on the following pages. 



The improvement in industrial conditions early in the year made it 

 possible to secure supplies and appliances not available during the 

 war, although standardized instruments urgently needed in many 

 fields of work are not yet readily obtainable. On the other hand, cer- 

 tain processes developed in connection with military activities are 

 proving to be of value in facilitating research, as, for example, in the 

 production of helium, the experimental use of which with organisms 

 is described for the first time. 



The earlier plans for field work in the arid regions of the Southwest 

 have necessarily been curtailed and modified by the continuance of 

 conditions along the Mexican boundary, which lies 60 miles to the 

 southwest of the Desert Laboratory. Material for the solution of 

 many major problems in phytogeography may be obtained only by 

 free access to the regions between our base and the Gulf of Cahfornia. 

 Meanwhile, geographic work has been continued on the Californian 

 coast and in a coastal mountain range and in Australia. 



GROWTH AND HYDRATION. 

 Character of Protoplasm Fundamental to Growth, by D. T. MacDougal. 



In my extended studies on growth, it has been necessary to go behind 

 current assumptions as to the composition and nature of protoplasm 

 and reconsider the data in older chemical determinations and to have 

 new analyses made. Living matter, of course, may not be subjected 

 to an analysis hke a sample of ore or a mixture of salts, but its actual 

 constitution must be inferred from the substances which may be 

 obtained by chemical treatment. Its essential components are pro- 

 teins, pentosans, lipins, and salts. The substances of the first two 

 groups are of especial importance and together make up all but the 

 minutest portion of protoplasts. The proportion which these two 

 substances bear to each other largely determines the character of the 

 living matter in any cell or in any organism. 



The protoplast of the animal is highly proteinaceous, and this 

 is also true of spores, bacterial cells, etc., in plants. The plant cell is 

 mainly characterized by a predominance of pentosans. The metabo- 



* Situated at Tucson, Arizona. 



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