IOWA ACADEMY OF SCIENCES. 
107 
connection. McGee^ says: “The macroscopic characters of the 
deposit are moderately constant: 
“(1) It is commonly fine, homogeneous, free from pebbles 
or other adventious matter, and either massive or so obscurely 
stratified that the bedding plains are inconspicuous; (2) it com- 
monly contains unoxidized carbonate of lime in such quantity 
as to effervesce freely under acids; (3) it frequently contains 
nodules and minute ramifying tubules of carbonate of lime; (4) 
in many regions it contains abundant shells of land and fresh 
water moUusca; (5) is commonly so friable that it may be 
removed with a spade or impressed with the fingers, yet it 
resists weathering and erosion in a remarkable manner, stand- 
ing for years in vertical faces and developing sieeper erosion 
slopes than any other formation except the more obdurate clastic 
or crystalline rocks.” McGee also states that it is a fallacy to 
regard the loess as identical in composition or that it is identi- 
cal in genesis or even in age. As to its origm, Chamberlin and 
Salisbury find that in western Wisconsin and contiguous 
parts of Illinois and Iowa its composition varies in different 
localities with that of the associated drift and that both compo- 
sition and distribution point to glacial silt as the parent forma- 
tion of the loess in the upper Mississippi valley. Prof. McGee 
in speaking of the plants of the loess in northeastern Iowa lays 
stress on the prevalence of hard wood forests in the area. That 
the timber belt is confined to this area. The chief trees of this 
region from my observations are, oaks a half dozen species 
{Quercus macrocarim, Q, coccinea, Q. tinctoria, Q. ruhra, Q. alba, 
Q. Muhlenbergii^ Q. bicolor). The Q bicolor is however, a swamp 
species. The latter and Q. MuJilenbergii are southern species 
that have extended northward along the Mississippi. The 
butternut {Juglans drier ea) of the uplands and walnut {Juglans 
nigra) of the bottoms, the former is northern and the latter 
southern. The genus Primus is represented by three species 
{Prunus Americana, P. serotina, and P. Virginiana). The crab- 
apple {Pyrus coronaria) is found everywhere in thickets. The 
white birch {Betula jiapyracea) is a rare tree, the river birch 
{Betula nigra) is abundant along the streams; other trees along 
streams are honey locust {GleditscMa triacanthos); sycamore 
(Platanus occidentalis) Kentucky coffc^e tree (Gymnocladus Cana- 
densis), all southern representatives. The elms are represented 
3The Pleistocene history of northeastern Iowa, Eleventh Ann. Rep. U. S. Geological 
Survey, p. 291. 
