32 
THE PLANT WORLD. 
coccinea. The Prunus serotina and Acer nigrum are common on 
the slopes of the hills. There are a few scattered groves of 
Pirns- strobus along the Yellow and Upper Iowa rivers. They 
are found on the limestone and sandstone ledges. We were par¬ 
ticularly interested in the plants found along the Yellow River 
near its source. Through the kindness of Hon. Ellison Orr, of 
Postville, I made a hasty study of one of the most remarkable 
spots in Iowa or in any of the neighboring states. Some of the 
plants found here occur in abundance in some parts of Wisconsin 
Fig. 12.—A group of Balsam Firs, with one White Pine to the left, and 
several small White Birches in the foreground. Undergrowth consists of 
Aconitum uncinatum, Viola blanda, Diervilla tridda, Pyrus arbutifolia, 
Cornus circinata and Corylus rostrata. Photo by L. H. Pammel. 
and Minnesota, but they are rare for this section of the country. 
It is therefore worth while to record a few of the plants found 
here. 
The balsam fir (Abies balsamea ) is common of course in 
northern Wisconsin and Minnesota. It does not occur in the 
