84 IOWA ACADEMY OF SCIENCES. 



are reached it gradually diminishes in numbers. It needs a much richer 

 soil than the Butternut. 



The Cottonwood {Poindus monilifera. Ait.) gi'ows abundantly along the 

 Mississippi river in bottoms, where both sandy and rich soil seem favorable 

 for its development, and the trees are often of very large size. They are 

 seldom found, however, on the uplands away from the streams except as 

 recent introductions. The species is now sometimes found in the neighbor- 

 hood of stone quai-ries in the loose clay soil. Trembling Aspen {Fopulus 

 tremtiloidcs, Michx.) is common in the rich, black soils of second bottoms, or 

 the humus soil on the ridges. Near Dubuque it occurs around rocky ledges. 

 The species grows in groups, sometimes several acres in extent. It is a 

 short-lived tree, and is followed by more useful tx-ees, like the Oak. The 

 Large Poplar (P. grandidentata, Michx.) is less common than the last. It is 

 found in more or less isolated groups in sandy and clay soils, and its growth 

 is more rapid than that of the Trembling Aspen. 



A few trees of the Sycamore (Platamis occidentalish.) were observed at 

 Turkey River Junction, Iowa. From this point southward it is moi*e fre- 

 quent in the Mississippi river bottoms. 



The Hackberry [Celtis occidentalis, L.) occurs in rich soil of the bottoms of 

 Root river and other streams; and not infrequently it is found on the rocky 

 limestone cliffs, as at North McGregor, Iowa. It is a tree which can adapt 

 itself to a variety of soils, and when cultivated does admirably on poor, sandy 

 soil. 



The Birches are fairly well represented, the most common species being 

 the River Birch [Betula ingra, L.) It, with the Soft Maple, more typifies the 

 timbered region of the Mississippi bottoms than any other tree. The Red, 

 or River Birch, diminishes in numbers southward. The Canoe Birch [Bet- 

 ula papyrif era, Michx.) is common about La Crosse and Trempleau, Wiscon- 

 sin, where it is usually found on the tops of the limestone bluffs, though 

 also occurring in ravines and ridges as well as in sandy soil. On some of 

 the rocky hills it is almost the only tree. It rarely attains great dimensions, 

 except when growing in rich clay soil. Near Dubuque it is scarce. Mr. 

 Reppert reports it from Muscatine; how much farther south it occurs in 

 Iowa, I have not learned. 



Yellow or Gray Birch {B. lutea, Michx.) is found more abundantly along 

 the sandy, rocky cliff's of the Kickapoo. It also occurs near a Tamarack- 

 swamp not far from La Crosse. It is not a common tree. 



Quite a grove of small Kentucky Coffee-trees [Oymnocladus dioicus,L., 

 Koch.) occurs south of La Crescent, in the Root river bottoms, and on the 

 Wisconsin side there are two or three trees about seven miles below 

 La Crosse. They are from twelve to fifteen feet high. The species is much 

 more numerous on steep hillsides near North McGregor, but none of the 

 specimens are large. From this point southwai'd it is more numerous. I 

 noted it at Clayton, Tui-key River Junction and Dubuque. It does not occur 

 in the interior of the country east of La Crosse, although I have seen it cul- 

 tivated in Madison, Wisconsin. 



The Honey-Locust ( Gleditschia triacanthos) was observed near Turkey River 

 Junction, Iowa, though it occurs as far north as McGregor and perhaps 

 further. It is occasionally cultivated in La Crosse. A fine tree occurs on 

 Mississippi street, near Western avenue. 



