214 THE GEOLOGY OF MINNESOTA. 



[Trees and shrubs. 



the same aspect is sometimes encountered to the depth of over one hun- 

 dred feet. 



In the valley of the Root river, and also along the Mississippi, the soil 

 of the alluvial terraces, greatly resembling that of the loam in the uplands, 

 is apt to be more sandy, and sometimes becomes very light and very poor. 

 These materials are generally seen to lie in obliquely stratified layers, and 

 to embrace, in the Mississippi valley, small gravel stones of northern origin. 

 The immediate flood-plain of these rivers presents still another variety of 

 soil. While it is generally sandy, and often very light, it is also a very rich 

 soil, and is apt to be enduring by reason of the Nile-like overflows to which 

 it is subjected, and the decomposition of large quantities of vegetation. 

 This variety of soil sustains some of the heaviest forests to be found in the 



county. 



Trees and shrubs. The county is supplied with plenty of timber for 

 fuel, and with some that is useful for lumber. The following list com- 

 prises a nearly, if not quite, complete catalogue of the trees and shrubby 

 plants of the county. 



Quercus coccinea, Wang., var. tinctoria, Bart. (Black oak). 



Quercns macrocarpa, Michx. ( Bur oak.) 



[These two oaks are common in the uplands. As brush and small trees they often form 

 thickets. There seem to be two varieties of the former in some places, but in others the char- 

 acters are blended in one. There is a plain popular distinction between the red and the black oak, 

 and solitary trees of the latter are often seen of large size standing in the midst of brush, belong- 

 ing apparently to a former forest growth now destroyed, and at the same, time this species is very 

 abundant as small trees or underbrush, often presenting some of the popular characteristics of 

 the red oak. The red oak is a graceful, open tree with smoother bark and larger leaves and acorns 

 than the black oak. 



Quercus alba, L. (White oak). 



Quercus rubra, L. (Red oak). 



Populus tremuloides, Michx. (Aspen). 



Populus grandidentata, Michx. (Great- toothed poplar.) 



Populus monilifera, Ait. (Cottonwood.) 



[Of these poplars the first two are by far the most common, but in proportion to their numbers 

 make fewer large trees than the last. They rarely exceed six or eight inches in diameter, while 

 the cottonwood sometimes becomes two or three feet in diameter, as seen in the Root river valley 

 at Houston. The cottonwood has a rough bark. The bark of the aspen may be distinguished 

 from that of the great-toothed poplar at a distance by the fact that the former becomes white, or 

 mottled with white, as the tree gets the size of three or four inches in diameter, while that of the 

 latter maintains its greenish or dingy-yellow color.] 



Populus balsamifera, L. (Balm of Gilead). [Common in cultivation. There are some fine 

 large trees of this kind at Mr. Powlesland's, sec. 36, Crooked Creek.] 



Populus dilatata, Ait. (Lombardy poplar). [Only seen in cultivation.] 



Acer rubrum, L. (Red maple). 



Acer saccharinum, Wang. (Sugar maple). 



Acer saccharinum, Wang., var. nigrum, Gray. (Black sugar maple). [Sometimes known 

 as rock maple.] 



