CORRELATION OF DISTRIBUTIONAL FEATURES. 541 



Pinus contorta (fig. 49).— The range given for this tree is based on 

 the view that it is identical with Pinus murrayana, and comprises the 

 regions that are occupied by the two forms— the northern Pacific coast, 

 the Sierra Nevada, the northern Rocky Mountains, and the Black 



Hills. 



The extremes and amplitudes of conditions for this tree are very 

 similar to those for Pseudotsuga mucronata. It encounters a slightly 

 greater number of hot days, and a greater value for the physiological 

 temperature summation, with a lower maximum value for the number 

 of days in the longest dry period. Pinus contorta is like Pseudotsuga 

 in encountering a wide amplitude of nearly all of the conditions here 

 studied, its strongest control appearing to lie in the number of hot 

 days and the values of the physiological summation of temperatures. 



It will be noted that both the eastern and western evergreen needle- 

 leaved trees are confined to ranges which exhibit a narrow amplitude 

 in the number of hot days. The amplitude of the physiological summa- 

 tion is narrow for all except the species that are found in the South- 

 eastern Evergreen Mesophytic Forest (for example Pinus echinata). 

 With respect to both of these conditions there is a marked contrast 

 between the evergreen needle-leaved and the deciduous broad-leaved 

 trees. 



TCMPtRATURC 



Days in Normal Frostcc** Season (f. S.> 



Hot Davs. F. S. 



Cold Oav«, F. S. 



Physiological Summation. F. S. 



Normal Dailv Mcan. coldest 14 davs or Year 



Normal Daily Mean. Year 



Precipitation 

 Normal Daily Mean. F. S. 

 Days in lonccst Normal Rainy Period. F. 5. 

 Days m longest Normal Dry Period, F. S. 

 Mean Total. Year 



£varoration 

 Daily Mean, 1887-8, F. S. 



Moisture Ratios 

 Normal P/t, F. S. 

 Normal n/Z, F. S. 

 Normal P/E, Year 



Humidity 

 Normal Mean. F. S. 



Sunshine 

 Normal Daily Duration. F. S. [3BB MB8B^^ 8i£ggB nnkn»WT i Mg-n i >7^ 



Moisture*Temperatur£ Indices 

 Normal P/E x T, F. S., Physiological Method ej^^B^^MBMMWB 



Fig. 49. Climatic extremes for Knus contorta. 



Pinus echinata (fig. 50).— The range of this tree occupies all of the 

 Southeastern Evergreen Mesophytic Forest except a strip along the 

 Gulf of Mexico and peninsular Florida, and also the southern half of 

 the Deciduous Forest region. It therefore exhibits amplitudes and 

 extremes which lie between those of the two vegetations in which it 



