512 CORRELATION OF DISTRIBUTIONAL FEATURES. 



tation has been recorded at Fort Bragg, California, where the condi- 

 tions and vegetation of the ocean front are more nearly those of the 

 Hygrophytic Forest than of the western section of the Mesophytic 

 Forest. At stations just inland from Fort Bragg the fr«>stless season 

 is about 100 days shorter. The number of hot days ranges from to 

 105, which is about one-third of the ampHtude for the entire country, 

 and the number of cold days ranges from 78 to 149 + , closely approach- 

 ing the maximum values, which occur in the Grassland. The physio- 

 logical summation of temperature has a relatively narrow amplitude, 

 from values approaching the minimum to 9,921 at Grand Junction, 

 Colorado, a station which must be regarded as approximating the 

 conditions of the forests in that vicinity. Much higher values of the 

 physiological summation might be expected for stations located in the 

 more southern extensions of the Mesophytic Evergreen Forest, but 

 our data fail to bear out such an expectation. Santa Fe, New Mexico, 

 is located close to bodies of Mesophytic Evergreen Forest, and is so 

 situated as to enjoy higher temperatures than the forest, yet the sum- 

 mation for Santa Fe is only 5,350, a figure considerably below the 

 maximum at Grand Junction. Flagstafif, Arizona, which is situated 

 in the midst of forest, has the very low summation of 2,652. The cold 

 nights of the mountain altitudes at which the Mesophytic Forest of 

 New Mexico and Arizona occurs are responsible for low daily mean 

 temperatures, and consequently for low values of the sunmiations for 

 the frostless season. 



The normal daily mean for the coldest 14 consecutive days of the 

 year is a condition ranging through a moderate amplitude and reaching 

 extreme values which are neither very high nor very low, overlapping 

 with the conditions in the Hygrophytic Forest. The normal daily 

 mean temperature for the year is of wide amplitude, but also fails to 

 attain the extremes for the country. 



When the climatic extremes for the precipitation conditions are 

 compared, as a whole, with those for the temperature conditions, the 

 former are seen to be of narrower amplitude, which points to the 

 Hmitation of the western section of the Mesophytic Evergreen Forest 

 as being due more largely to moisture conditions than to those of 

 temperature. This is confirmed by the narrow amplitude of the 

 moisture ratios, at least of those which relate to the frostless season 

 only. Although the actual extremes of the moisture ratio tt/E for the 

 frostless season are 0.12 and 0.60, it will be seen by an examination of 

 plate 59 that the major portion of the western Mesophytic Forest is 

 comprised between the lines for values of 0.20 and 0.40. The lowest 

 evaporation values and the highest relative humidities for this region 

 are recorded for the extreme coastal stations of northern California, 

 and they are not typical of the great bulk of the forest, although they 

 permit its occurrence in a form approaching the character of the North- 

 western Hygrophytic Forest. 



