128 IOWA ACADEMY OF SCIENCE Vol. XXV, 191S 



Sumach, Rhus glabra Linnaeus. Common. 



Poison ivy, Rhus toxicodendron Linnaeus. Common. 



Wahoo, Evoni/nius atropurpiireus Jacquin. Not common except at 

 a few spots on Mormons Ridge. 



Bittersweet, Celastrus scandens Linnaeus. Quite common. 



Maple, Acer saccharum Marshall. Cultivated very commonly, es- 

 pecially along the streets of Marshalltown. A few found along the 

 river may be native. 



Soft, or white, maple, Acer saccharinum Linnaeus. One of the most 

 common lowland trees. 



Box elder, Acer Negundo Linnaeus. Also common along river. 



Woodbine, Psedera guinquefolea Linnaeus. Common. 



Frost grape, Vitis vulpina Linnaeus. This seems to be the common 

 wild grape, although others may occur. 



Red-osier dogwood, Cornus stolonifera Michaux. Common Corn us, 

 but others probably are present. 



Green ash, Fraxinus peTinsiilvanica var. lanceolata (Borkhausen) Sar- 

 gent. Common. 



Black ash, Fraxinus nigra Marshall. Not common. 



Honeysuckle, Lonicera dioica Linnaeus. Not common. 



Wolfberry, Symphoricarpos occidentales Hooker. Frequent. 



Sheepberry, Viburnum lentago Linnaeus. Uncommon. 



Elderberry, Sambiicus canadensis Linnaeus. Common. 



The timbered area is almost wholly confined to the valleys of 

 the various streams and to the upland immediately adjacent. It 

 is divided into two rather sharply differentiated groups : An 

 upland form, in which oaks, hickories, ironwood, and Avild cher- 

 ries (particularly P. pennsylvanica) predominate; and the river 

 bottom group, containing as the most conspicuous forms, willows, 

 cottonwoods, elms, ash, maples, and hawthomes. Aside from 

 this the country-side is dotted with groves about nearly every 

 gToup of farm buildings. The trees in these groves vary greatly, 

 but perhaps maples, willows, and the various conifers are more 

 often planted than any others. Hedges of osag: orange [Maelura 

 pamifera (Raf.) Schneider) are found occasionally along the 

 country roads. Several groves of catalpa also remain from a 

 craze for catalpa planting which swept over the country a few 

 years ago. They were planted as C. speciosa but as a matter 

 of fact the majority of them proved to be C. hignonio'des Avhich 

 winterkilled to some extent in this region. 



Outside these wooded areas practically the entire surface of 

 the county is under cultivation, the principal crops being corn, 

 oats, and clover, althoug-ih many others are cultivated to some 

 extent. This condition of affairs has quite a marked influence 



