44 CARNEGIE INSTITUTION OF WASHINGTON. 



part in 3,200 a month later, and then rose in midsummer to 1 part in 2,500. 

 The trunk of a dead tree does not show such variations of a magnitude within 

 the range of the instruments. 



Defohation of the Monterey pine early in the season caused a stoppage 

 of growth, while such defoliation in June had but little effect. Decapitation 

 of the trunk within a meter of the dendrograph caused a stoppage of growth, 

 although the stump bore many active leafy branches. These and other 

 experimental tests are being extended and repeated before interpretations 

 of their effect on the mechanism of food transport are attempted. 



Young trees of the Monterey pine, growing near the Coastal Laboratory, 

 which exhibited interrupted impulses in enlargement of the trunks in Decem- 

 ber, began growth more steadily in the first week in January and continued 

 in the cases of Nos. 16. 17, and 20 until the end of October. The period 

 of growth thus exemplified amounted to about 300 days, which is the 

 longest yet recorded for any tree of which an accurate record has ever been 

 made. The common conception that trees in the tropics are actively growing 

 throughout the year has not been confirmed nor adequately tested. 



By the cooperation of Mr. G. A. Pearson, of the Forest Experiment Station 

 at Fort Valley, near Flagstaff, Arizona, dendrographs have been operated 

 on two trees of Pinus scopulorum at an elevation of about 7,000 feet. The 

 behavior of the yellow pine has thus been followed on the slopes of Pike's 

 Peak in Colorado, on the crest of the Santa Catalina Mountains in Arizona, 

 and on this elevated plateau at the place noted. These results have a special 

 interest, since trunks of this pine are being used as records of climate in 

 studies of the remains of the peoples who inhabited the region during the 

 last 1,000 or 2,000 years. 



Stem Analysis of Monterey Pine and Redwood, by Forrest Shreve. 



The records embodied in the annual rings of trees form excellent material 

 for investigating the relation of environmental conditions to the yearly march 

 of growth. The use of the records of certain long-lived trees as criteria for 

 interpreting the climatic conditions of the remote past makes it important 

 to determine the influence exerted upon growth by the conditions of the more 

 recent past, for which we have climatological records. These considerations 

 have led to a continuation of work on the Monterey pine and redwood in 

 the vicinity of the Coastal Laboratory. 



Further work, including the bisection and detailed measurement of the 

 trunk of a second pine, has shown a very close correspondence between the 

 course of the growth graph based on stump measurements and that based on 

 the average of 10 transverse sections in the lowest 30 feet of the trunk. This 

 strengthens the reliability of data from the stump section alone as a criterion 

 of the performance of the trunk as a whole. 



The course of growth has been measured for 6 small trees and 4 large ones 

 growing under identical conditions in close proximity to the rainfall station 

 at Carmel, The trees in each group were selected for similarity of size and 

 crown development, those in the small group still having the excurrent crown 

 indicative of active growth. In these trees growth was correlated with the 

 rainfall for December to September, inclusive, a period which covers the 

 growing-season of the pine and one preceding month. Correlations were 

 made from graphs of growth and rainfall and were regarded as positive in cases 



