172 BULLETIN 1059, U. S. DEPARTMENT OF AGRICULTURE. 



writers know of no single method or basic method of following these 

 reactions which promises more than the method of following the 

 plant's condition by frequent observations on the osmotic pressure 

 or sap density. In the case of trees, the termini should of course be 

 studied, but it is probable that valuable supplemental data can be 

 obtained at one or two points along the stem and on side branches. 

 Through this method, with any individual tree, it may be possible to 

 depict the sudden influx of sap in the spring, which precedes the first 

 growth; the gradual increase in carbohydrates as the new tissues 

 continue to function, and temporary changes due to water supply 

 and water loss. Possibly the end point of the season's photo-synthetic 

 activity may be found, if there is any; the same method will show 

 the changes which the tree undergoes through the winter. In addi- 

 tion to osmotic pressures, the starch content of leaves should be 

 examined from time to time. It is self-evident that these data can 

 only be interpreted when correlated with observations on both the 

 soil and atmospheric conditions. 



A method which would show the rate at which the tree is being 

 supplied with water would be a valuable adjunct to the above; but 

 no attempt of this nature is known, beyond transpiration studies. It 

 is possible, however, that a means may be devised by which this rate 

 may be directly determined. There is room for a great deal of de- 

 velopment in these lines. 



FIELD OBSERVATIONS, PHOTOGRAPHS, AND MAPS. 



The " Daily Observations " form in the series for climatological 

 studies, intended for field observations, is thought to be adapted to 

 universal use. It is of a size to fit Forest Service loose-leaf notebooks, 

 6f by 4 inches. It contains lines for all factors on which regular ob- 

 servations are likely to be taken. It has five vertical columns, which 

 may be used for five stations visited consecutively on the same day, or 

 for a single station visited for five consecutive observations. In the 

 first instance the numbers of the stations would be stamped at the 

 heads of the several columns and the date would be stamped at the 

 bottom. In the second instance the days of the month would be 

 stamped at the heads of the several columns and the month and year 

 at the foot of the form. In either case the exact time of observation 

 should be entered in the second line of each column. Since observa- 

 tions at completely equipped stations may take from 10 to 20 minutes, 

 the time entered for such stations should be, as nearly as possible, the 

 time of reading current temperature and anemometer, these condi- 

 tions being subject to considerable changes in a few minutes. 



Each point chosen as a site for ecological study should, in addition to 

 a complete description 23 of the features which may influence soil qual- 



13 The " Description " form is suggestive. 



