22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, I40 



time and amount of diameter growth, as well as to observe regenera- 

 tion of living tissues. 



In November 1939 nine trees (three ponderosa pines, three loblolly 

 pines, and three Arizona cypresses) were moved from the grounds 

 of the Texas Agricultural Experiment Substation to large cans in the 

 Conservatory of Texas Technological College. In April 1940 they 

 were transplanted to the grounds of a private residence a half mile 

 from the College campus. These trees were kept under constant ob- 

 servation and measurement until the last of them was cut down and 

 dissected in May 1944. 



Increment cores were not used in our work. In fact, our methods 

 were designed especially to avoid their use because it was learned 

 early in the work that a core, as one radius, is wholly inadequate to 

 give a picture of the growth-layer pattern throughout a trunk or 

 branch under extreme lower forest-border conditions. 



MICROSCOPIC METHODS 



In all cases, branches were cut from the trees by means of a fine- 

 toothed coping saw. Blocks suitable for immediate sectioning with a 

 microtome, or for storage in a formalin-acetic-alcohol fixing agent for 

 future sectioning with a microtome, were removed from the branches 

 in the laboratory with the same saw. Wherever possible, a set of two 

 blocks was taken from each locality on a branch so that both cross 

 and longitudinal sections could be made. The number of branches re- 

 moved from an individual tree varied from i to 43, dependent upon 

 the purposes of the experiments. The number of blocks taken from 

 a single branch varied from i to 17, counting only the blocks taken 

 for cross sections. 



In the entire project, a total of 433 branches and 5 main trunks 

 were brought to the laboratory. As a matter of passing interest, we 

 may mention that 1,245 blocks were taken from these branches and 

 trunks for the purpose of cutting cross sections, and 553 blocks were 

 also taken, from which both radial and tangential sections were cut. 



A table microtome, used during the early part of the project, was 

 soon superseded by a sliding microtome. The thickness of the sections 

 varied with the type, size, and condition of the materials and averaged 

 about 30 microns. All staining was done with safranin and fast green. 

 Counting cross, radial, and tangential sections, slides totaled some 

 2,500 in number; however, for the purposes of the present report, 

 we concentrated on cross-section slides from 1,500 blocks. 



The wood blocks were ordinarily not softened before sectioning 



