214 NINETEENTH REPORT. 



Greenfield, the forest is composed of Planatus occidentalis, Ulmus 

 amer'icana, Acer saccharinum, Fagus grandifolia, Fraxinus nigra, Quercus 

 bicolor and Carpinus caroliniana, in order of relative abundance. The 

 stand is of tyi)ical density, tlie trees standing an average distance of twelve 

 feet apart, showing a fair amount of tolerance for this species. But the 

 tree invariabl}'^ forms forests in physiologically wet habitats, on clay, 

 loam or shallow sand, with or without humus, associated with hydrophytic 

 species. It shows no tendency to form forests in the black oak habitat, 

 although tliis forest is open and there is plenty of chance. The results 

 do not sustain the conclusions of Griggs,* who has overlooked the fact that 

 one of the crucial tests of a forest type is its ability to reproduce. The 

 constant appearance of sycamore in the hydrophytic forests of the old 

 lake bed area is one of the distinguishing features of this forest in south 

 east Michigan. The sycamore is also abundant on the flood plains oi both 

 the Huron and Rouge Rivers. 



III. Species tending to form unlike-commensal forests. 



Under this head are included those characteristic trees which, of them- 

 selves, show little or no tendency to occur in pure growth, but occur in 

 association witli other species. These are the beech, silver maple, and 

 sassafras, each associating with certain other species and characterizing 

 three different portions of the county. The forests characterized by each 

 of these trees, respectively, are at once the largest and most characteristic 

 types east of the Defiance Moraine. Together they are estimated to cover 

 over 70 per cent, of the county. The silver maple occurs as the character- 

 istic tree of tlie mixed forest on the flat, wet, and poorly drained glacial 

 cla}', or till j^lains, of the extreme eastern portion of the county, forming 

 a belt extending north and south, at or near the shore line, and spreading 

 inland a distance of one to seven miles. The belt covers Gratiot town- 

 ship and most of Grosse Point, city of Detroit, Springwells, Ecorse, 

 and a portion of Monguagon and Brownstown. Gratiot, witli an average 

 slope of eight feet per mile, and Ecorse, with a slope of four feet per 

 mile, and part of Detroit, with a slope of three feet per mile, afford 

 ideal conditions for the growth of this forest. 



The forest is quite uniform in composition, the numerous lists taken 

 from different wood lots tliroughout the belt, showing a remarkable 

 similarity in composition and relative abundance. The silver maple often 

 forms over 50 per cent, of the stand. One wood lot listed in 1903 had nine 

 species on one-fourth acre, in which tlie silver maple formed 71 per cent, 

 of tlie stand. The most common secondary species of trees are Ulmus 

 americana, U. fulva, Fraxinus pennsylvanica, F. pennsylvanica var. lan- 



*Ohio Biological Survey, Bulletin 3, page 2D5. 



