DEPARTMENT OF BOTANICAL RESEARCH. 



D. T. MacDougal, Director. 



The general conditions affecting the activities of the Department 

 have made it seem advisable to collate and summarize the results of 

 all work in a stage sufficiently advanced to justify pubhcation. Mem- 

 bers of the staff, therefore, have narrowed the scope of their experi- 

 mentation and devoted attention chiefly to the preparation of manu- 

 scripts. Exploration and field work have been reduced to a minimum, 

 the chief effort in this direction being the desert studies in AustraHa 

 begun by Dr. W. A. Cannon in May 1918, and the survey of the Santa 

 Lucia Mountains, a coastal range running southward from the Coastal 

 Laboratory, by Dr. Forrest Shreve. Collaboration with workers 

 outside the Institution has been less than in any preceding year. 



As may be seen, much attention has been devoted to the study of 

 fundamental problems in carbohydrate metaboHsm and to the imbi- 

 bitional action of the plant colloids in growth. All of the water- 

 relations of organisms have necessarily been taken into consideration. 

 An adequate physical explanation of the origin and action of the 

 spinose and succulent plants constituting the characteristic desert 

 vegetation has been found. Important geographic and ecological 

 results have been formulated as described in the following paragraphs. 



IMBIBITION AND GROWTH. 



Development of Conceptions included in Growth, by D. T. MacDougal. 



Three main conceptions concerning growth and its developmental 

 aspects in plants are to be met in the history of physiology in the last 

 half century. The first or earliest, that of special stuffs or substances 

 which come in the developmental and seasonal crises and which were 

 taken to be necessary for growth and for the origination and develop- 

 ment of reproductive organs or of any bud, is now replaced with the 

 modern conclusion that "formative" material as such has no actual 

 existence and no good basis in theory. The present trend of thought 

 leads to the assumption that growth proceeds from and depends upon 

 states, or combinations, or accumulations in connection with hving 

 matter rather than any ineffable differentiated stuff or substance. 



The second aspect of the subject was that which deals with the 

 incorporation of new material in the cell and its subsequent distention. 

 The protoplast is currently dealt with as a tonoplast, the center and 

 seat of energy in this connection being the vacuole, while an indis- 

 pensable organ in this conception of the cell is an ideal "semiperme- 

 able" membrane, acting on the basis of the fundamental researches 

 of Pfeffer and de Vries. 



The third group of inquiries has been directed toward measure- 

 ments for the purpose of establishing the physical constants of growth. 



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