study. An examination of the plant and. olimatic graphs 

 fto "be considered later) ^;ill f=hOT)7 that the plant values for 

 most of the stations rise above the temperature efficiency 

 values in the middle of the season, and fall below theqi at 

 its end. This is probably due in part to the effect of ligh^ 

 and evaporation as will be brought out below, in ^.^-' "i i scus- 

 sion of the plant data, but it may also be related to an in- 

 adequacy of the temperature efficiency values to represent 

 the actual effectiveness of temperature in growth control. 

 It appears to be at least suggested that the actual tempe- 

 rature efficiency "alues for these soy-bean ilants increase 

 m.ore rapidly with increase in the temperatue itself, ior the 

 range here encoiintered (between 40*^ add So""?. ) , than lo the 

 physiological index values derived from Lehenbauer's study 

 of mSulize seedlings. This whole question deserves much more 

 epxf^^rimental study. It is a surprising fact that we have 

 available only a single thoroughgoing investigation of the 

 relati on of temperature to the growth of higher plants, in 

 spite of the fact t'nat the primary importance of the tempe- 

 rature control of growth is obvious to every observer and has 

 long been qualitatively appreciate!. A com.parison, for any of 

 the stations employed, of the range of growth values for the 

 plants with the remainder sura^^atlon values for temperature 

 (which ar- practically equivalent to the exponential summa- 

 tion values in this study) and with the physiological summa- 

 tion indices will furnish evidence for the verification of 

 these sta*:ements. '^he graphs 6'f the physiological sumniati on 

 indices of temperature efficiency shofi much steeper slopes 

 than do the corresponding graphs derived from the other two 



