IOWA ACADEMY OF SCIENCES. 81 



said that certain species, strictly confine themselves to certain detinite soils, 

 yet certain trees, as well as herbaceous plants, may preponderate in certain 

 soils. Perhaps this may be due to the physical condition of the soil, rather 

 than its chemical constitution. 



The Soft Maple [Acer saccharinum, L.), Red Birch [Betula nigra, L.), are the 

 predominating trees in the Mississippi, Wisconsin and Black river bottoms. 

 They also follow up the smaller streams which tlow into these rivers, but as 

 soon as these streams are left these trees become rare. The Soft Maple and 

 Black Birch occur most numei'ously where the lands are subject to overflows 

 every year. Most of the Oaks never occur in such situations, yet the Swamp 

 White Oak [Quercus Oicolor, Willd.) is an exception. 



The only place where this species occui-s is in the low, sandy and black 

 bottom lands of the Mississippi and Black rivers. The White Pine only 

 occurs in the sandy rocks or sandy loam soil of the region, always near 

 streams, but in the northern part of La Crosse county it is encroaching on the 

 loamy soil. The Tamarack {Larixlarcina) only occurs in cold, wet swamps 



The soils of the region may be classed under sandy, loamy, calcareous, 

 alluvial and peaty. The greatest areas of sandy soil occur near the mouths 

 of the rivers. (This is not true for the interior of the State.) These sand 

 prairies are not, however numerous on the west side of the river. As an 

 illustration, at La Crosse, Wisconsin, there is a sand prairie some eight 

 miles long and from one-half to three miles wide. The only arboreal vege- 

 tation growing on these soils are two species of Oak, Burr Oak {Quercus 

 tnacrocarjm, Michx.), Black Oak(^. tinctoria, Bartram), and occasionally 

 the Green Ash {Fraxinus viridis, Michx.) and Black Birch {Betula lenla). 



These trees, however, only occur in close proximity to the Mississippi 

 bottoms. Other sand prairies similar to this one occur at Trempleau and 

 Prairie du Chien, Wisconsin. 



As regards the herbaceous vegetation on these prairies it might be said 

 that it is a typical prairie flora. Liatris cylindrica, Verbena stricta, Baptisia 

 leucantha, Petalosternon violaceus, P. candidus, Oenothera rhombipetala, Botc- 

 teloua hirsuta, B. racemosa, etc., occur very frequently, though the Sand 

 Bur {Cenchrus tribuloides) is the most characteristic plant where the soil has 

 been plowed or loosened by the winds. 



The calcareous soils occupy the tops of the hills and are of smaller extent 

 near La Crosse, Wisconsin, than Dubuque, Iowa. Birches, especially the 

 Canoe Birch {Betula papyrifera, Marshall), are a most marked feature of it- 

 but this species is by no means confined to soils of this character. Two 

 other plants only occur, so far as I have observed, in this region on the cal- 

 careous soils; they are Zygadenus elegans and Camptosorus rhizophyllus. 

 Loamy soils are by far the most abundant; they occur on the slightly rolling 

 ridges and in the valleys. The White Oak {Quercus alba, L.) grows excel- 

 lently in such soil. Alluvial soil does not occupy great areas, except at the 

 mouths of some rivers. The great bottoms of the Mississippi consist mostly 

 of a sandy soil, covered over in some places with a black, rich soil. The 

 White Elm, Box Elder, and Soft Maple are common. 



The peaty soils are impassable during early spring and summer. Few 



trees are able to grow — only an occasional Willow or Tamarack. The 



bulk of the vegetation consists of species of Carex and Scirpus. Now and 



then Lilmm canadense Cypripedium speclabile, or, here and there patches 



6 



