2 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9 
Geologically the Ozarks are complex; crystalline rocks are to be found 
in the southeastern part of the state, namely in the St. Francois Mountains, 
which are considered oldest. Further, several beds of limestone and sand- 
stone are to be met. The various systems are either Carboniferous, De- 
vonian, Silurian, Ordovician, Cambro-Ordovician, or Cambrian. 
Erosion has played an important part in the topography of the country ; 
therefore soil types are of various kinds and to a considerable extent derived 
from the various rocks in their respective environment. The physical 
properties of these soils greatly influence the development and the differenti- 
ation of the flora ; they are grey to reddish-brown in color, contain but little 
organic matter, often stones are present, and rock outcrops are very common. 
Level areas are the least stony as a rule. The reddish-brown soils are 
usually derived from cherty limestones of the lower Carboniferous group, 
the grey soils derived from the Cambro-Ordovician group being silicious 
limestones. The oxidation of iron gave to the soil a reddish-brown color, 
which is absent in grey soils of the cherty limestones. The character of the 
soil varies from a stony to a silt loam. 
Many streams and creeks traverse the country and are the cause of con- 
stant erosion, giving to a large extent the present aspect of the topography 
of the Ozarks. Outside the rainy periods they are harmless little streams, 
often entirely dry during the largest part of the summer; after heavy rains, 
or sometimes after sudden melting of a heavy snowfall, they grow to wide 
streams, overflowing the surrounding country and denuding areas of a 
part of the soil and vegetation, and often giving a different aspect to the 
environment. 
The climate of the southeastern part of Missouri is characterized by 
hot summers and mild winters. The temperature data which the writer 
was able to obtain are given in table i. 
Table i . Temperatures in Southeastern Missouri 
Month 
Mean 
Maximum 
Minimum 
° C. 
° c. 
° c. 
January 
~ I. II 
+ 3.33 
- 5 
February 
+ 0.55 
5-55 
- 3-33 
March 
8.89 
13-30 
-f- 2.78 
April . . . 
15 
20.55 
10.55 
May 
18.89 
25 
13.89 
June 
25 
31.10 
20.55 
July 
31.67 
40.55 
24.44 
August 
31. II 
38.89 
23.30 
September . 
24.44 
31.67 
20 
October 
16.10 
22.22 
II. 10 
November 
8.89 
16.11 
3-85 
December. . . 
5 
10 
- 0.55 
In the higher portions of the mountain ridges and peaks the temperature 
is lower. Considerable cold spells are of short duration; in some winters 
