DEPARTMENT OF BOTANICAL RESEARCH. 57 



GROWTH AND PERMEABILITY. 



Dendrographic Records of Growth in Trees, by D. T. MacDougal. 



The studies of the factors influencing growth in trees have been continued. 

 The records of the changes in diameter associated with growth in 12 trees 

 were recorded in 1921 and of 17 in 1922. There are now available the records 

 of 70 seasons' growth which were obtained by the use of the dendrograph on a 

 total of 20 species for one or more seasons. A continuous tracing of the 

 changes in diameter of Monterey pine No. 1 for four years beginning Septem- 

 ber 1918 is available and more attention has been devoted to this species than 

 any other. 



The individuals selected for the observations represent also certain condi- 

 tions of soil and exposure. Experiments in variations in water-supply, effects 

 of girdling, and decapitation, etc., have been made. With the numerous 

 improvements in design of the dendrograph by which the accuracy of this 

 instrument has been increased, it has been found possible to differentiate the 

 variations in the woody cylinder from those of the extreme outer layer com- 

 posed of the cambium, bast, and bark. Correlations between the variations 

 of the trunk and of the stomatal action and accompanying variations in trans- 

 piration have been established. 



The behavior of a walnut (Juglans major) in its native habitat at 7,000 

 feet, in the Santa Catalina Mountains, Arizona, and at the Coastal Laboratory 

 near sea-level, has been studied. 



The dendrograph has been successfully adapted to the measurement of the 

 variations in volume of the giant cactus (Carnegiea gigantea) of Arizona, 

 bringing to light some striking changes in volume which appear to be due to 

 different agencies from those which are operative in a woody trunk. 



The Artificial Cell with Biocolloidal Membranes, by D. T. MacDougal. 



The type of artificial cell described in the report of this Department for 

 1921 (see pages 57-59) has been used extensively in a study of the nature 

 of the exchanges between the living cell and its environment. In the earlier 

 use of the cell, and in obtaining the results which have been published pre- 

 viously, the cell was constructed with outer clay walls with the pores of such 

 a size that when filled with calcium chloride at 0.01 M a negative osmose 

 followed. 



The researches in hand require measurements of the possible action of the 

 actual constituents of the walls and outer layers of the plant cell. It was 

 therefore important to use material of approximately the same character in 

 the cell. The improved type was constructed as follows : A double thickness 

 extraction-thimble (Schleicher and Scholl or Whatman) 33 by 80 mm. was 

 taken to represent the denser skeletal part of the cell- wall. This was fitted 

 with a cork stopper through which were passed two glass tubes. One tube 

 was 3 cm. in length, 8 mm. internal diameter, and served as a filling tube. 

 The other tube was 8 cm. long, 5 mm. in diameter, and the free end was bent at 

 right angles and pointed, serving as a delivery tube. The thimble was dipped 

 in agar (4 per cent solution) at 90° to 100° C. until the wall was thoroughly 

 infiltrated. When this had cooled it was dipped in commercial alcohol which 

 precipitated the agar in the form of granules held in the meshes and on the 



