HARPER: BOTANICAL CROSS-SECTION OF MiIssIssIpPI 399 
climates evergreens abound in and near peat bogs and are scarce 
in clayey soils, and it is well known that potash is scarce in peat 
and abundant in clay. 
Just why potash should be antagonistic to evergreens is an 
ecological problem that need not.be discussed here; for at present 
I am merely pointing out the geographical correlation. The 
reasons why this correlation has not been made before are probably 
first because potassic rocks are not conspicuous and identifiable 
at sight like limestone, and second because the percentage of 
potash in the soil varies between much narrower limits than does 
that of lime, and most soils in inhabited regions have enough 
potash for the average plant. But it has been proved by many 
experiments that in an artificial soil containing no potash at all 
nothing will grow; and it is therefore reasonable to assume that 
between this artificial condition produced in the laboratory and 
natural soils containing an average amount of potash there must 
be intermediate stages where the vegetation is very different from 
what it is on the average soil. As potash seems to be more 
abundant in leaves than in any other part of a plant it is natural 
that a deficiency of this substance should manifest itself first in 
the leaves, and that plants which do not have access to much 
potash should have smaller leaves than those of rich soils, and 
keep them longer. 
GEOLOGICAL SURVEY OF ALABAMA, UNIVERSITY 
Explanation of plates 21, 22 
Fic. 1. Level dry woods about two miles north of Sheppardtown, Leflore 
County, approximately on the “ dogwood ridge.” The most conspicuous trees are 
Nyssa sylvatica (in foreground), Quercus nigra, and Ilex opaca. June 8, 1911. 
Fic. 2 at Quito, Leflore County, looking west from wagon bridge. 
Trees mostly Taxodium distichum and Nyssa uniflora. The dead branches in the 
water indicate the absence of current. June 8, 1911. 
Fic. 3. Eroding bank of Mississippi River on outer side of bend about two 
miles above Greenville, Washington County. Shows Taxodium distichum, Populus 
tern) bank of river a little farther upstream, 
June 10, rgort. 
Nearer view of same (eas 
showing numerous vines, Platanus occidentalis, etc. 
