Page:Popular Science Monthly Volume 84.djvu/434

430 base line twenty-five degrees below the upper limit of the temperature to be estimated, by arcs of the curves marking the hours, and by the crooked line traced by the pen as a result of changes in temperature, as shown on the accompanying sheet (Fig. 7).

The areas of such figures for temperatures is multiplied by the factor 4.5 for temperatures between 40° and 65° F., and by 20 for temperatures between 65° and 70° F., and by 45 for temperatures

 The solid line shows temperature effects in 1912, the broken line during 1913.

between 70° and 75° F., by 70 for temperatures between 75° and 80° F., by 78 for temperatures between 80° and 86° F., the optimum, etc. Time does not suffice to mention the necessary corrections, or the studies being made for the refinement of the method, but attention may be called to the estimation of the temperature factor by this method at our two main experimental localities during the first four and six months of two years at the Desert Laboratory, and the Coastal Laboratory (Fig. 8). The facts displayed in the accompanying figure go far to explain the divergent action of species under observation in the two places. Studies are now in progress for the redetermination of the factors expressing the rate of growth under the ordinary swing of daily temperatures and for an exacter application of the results.

There is much reason to believe that in the integration of the temperatures and moisture relations by the methods outlined we will be able to identify the causation of the remarkable evolutionary departures