IOWA ACADEMY OF SCIENCES. 107 



coDiiection. McGee^ says: "The macroscopic characters of the 

 deposit are moderately constant: 



"(1) It is cooamonly 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 lioae in such quantity 

 as to effervesce freely under acids; (3) it frequently contains 

 nodules and minute ramifying tubules of carbonate of lime; (4) 

 in manj^ 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 dt^veloping sleeper erosion 

 slopes lhan 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 orig'n, Chamberlin aid 

 Salisbury find that in western Wisconsin and contiguous 

 parts of lilincis 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. McGt e 

 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 tiees of this 

 region from my observations are, oaks a half doz m ppecif s 

 {Qvercus macrocarpa, Q. coccinea, Q. linctoria, Q. rubra, Q. alba, 

 Q. Muhlenbergii. Q. bicolor). The Q bicolor is however, a swamp 

 species. The latter and Q. MuhJenbergii are southern species 

 that have extended northward along the Mississippi. The 

 butternut {Jughms cinerea) of the uplands and walnut {Juglans 

 nigra) of the bottoms, the former is northern and the lattfr 

 southern. The genus Primus is represented by three species 

 {Prunus Americana, P. serotina, and P. Virginiana). The crab 

 apple {Pyrits coronaria) is lound everywhere in thickets. The 

 white birch {Betula ■papyracea) is a rare tree, the river birch 

 {Betiila nigra) is abundant along the streams; oilier trees along 

 streams are honey locust {Gleditschia triacanthos); sycaojore 

 {Platarius occidentalis) Kentucky coffee tree (Gijmnocladiis Cana- 

 densis), all southern representatives. The elms are represented 



•The Pleistocene history of northeastern Iowa, Eleventh Ann. Eep. U. S. Geological 

 •urvey. p. 291. 



