DRY FORESTS OF TENNESSEE VALLEY REGION. 81 
Pines are almost totally absent in this valley, and it is only at its 
western limit, and chiefly south of the Tennessee River, in Colbert and 
Franklin counties, where deposits of sandy loams and gravels overlie 
the Subcarboniferous strata, that the character of the forest flora 
changes by the appearance of the short-leaf pine among the hardwood 
trees. The climate of the valley is somewhat extreme. According to 
the observations of the United States Weather Service at Huntsville 
(altitude 650 feet), made during a period of fourteen years, the mean 
annual temperature is 59.9° F.; for the winter, 41°; spring, 5Y.9°3 
summer, 75°, and for the fall, 59.7°. The lowest temperature once 
during this period was 9° below zero; the highest, 96°. The average 
of annual minimum temperatures is 11°; the average of the highest 
temperatures, 92°. The range of temperature throughout the year is 
most clearly exhibited in the following table: 
Absolute and average minima and maxima. of temperature for each month, 
Month. Jan, | Feb. Mar. Apr. | May.|June. July.) Aug. sept.| Oct. | Nov.| Dec. 
| | | | | | 
OO 7 —) — | | | ~ ——- 
° ‘ | o | Oo ° o | o o | o i) ) 
Absolute minima ........- 9 7 8 | 18 31 36 51 54 39 29 13 7 
Average minima.......--- 14.4 | 12.2 | 19.5 | 34.8 | 45.8 | 51.9 | 59.8 | 58.2 42 34 21 15 
Absolute maxima.......-. 75 75 84 86 90 92 95 96 91 86 78 68 
Average maxima ......--- 68 70 80 2 86 90 92 90 86 81 72 76 
The mean annual precipitation is 54.1 inches; for the winter, 14.68; 
spring, 15.41; summer, 15.16; fall, 8.85.' 
VEGETATION OF THE TABLE-LANDS AND HIGHER RIDGES. 
Xerophile forests (cedar glades).—The limestone strata of the foot- 
hills which form the lower terraces of the higher ridges, undermined 
and dislocated by the action of water, are almost bare of soil. On 
these rugged grounds the red cedar (Juneperus virginiana) predomi- 
nates, but a few other trees gain a foothold. Among them is the blue 
ash (Fraxinus quadrangulata), a fine timber tree of the Alleghenian 
area, which reaches its southern limit here, where it is of stunted 
growth, being rarely more than a tree of medium size. A peculiar 
varietal form of the white ash (/rurinus americana curtissi) is not 
infrequently found with the last. It is readily distinguished by its 
low habit of growth, almost always beginning to branch below a height 
of 8 to 12 feet, the spreading branches somewhat drooping, the foliage 
pale, and the fruitsmaller. In this locality the seeds have the embryo 
well developed. This tree has also been found by Curtiss in the cal- 
careous hills of Eufaula, on the eastern border of the State, and is 
apparently not rare in the cedar brakes of central and southeastern 
Tennessee. 
1p, H. Mell, Climatology of Alabama, bulletin 18, Alabama ‘Experiment Station, 
new series, 1890, p. 23. 
15894——_6 
