MICHIGAN ACADEMY OF SCIENCE. 217 



sassafras or black oak associations, but sometimes with beech and red 

 maple. Also about one and one-half miles east of Plymouth, on the 

 south bank of the Rouge, we see in plain sight from the Wayne-Plymouth 

 electric line, a lone pine towering above the deciduous trees siirrounding. 

 This is a remnant of the white pine forest lumbered 28 years ago. There 

 are eleven stumps remaining to tell the story, indicating the trees were 

 127 years old when cut. There can be no question but that this was 

 original forest. 



SUMMARY AND CONCLUSIONS. 



Having now completed the salient feature of the forest vegetation of 

 the county, some of the more general interrelations existing between the 

 associations, as a whole, and the environmental conditions may be pointed 

 out. 



Throughout the investigation it has been plainly evident, from a care- 

 ful comparative study of the returns from the cultivated land in each 

 of the several forest associations, that land from which any given forest 

 association has been removed possesses agricultural possibilities distinct 

 from land from which some other forest association has been removed, 

 though the soil in the two areas, may look exactly alike. Such differ- 

 ences, clearly revealed by the vegetation and of extreme imjjortance 

 agriculturally, are as a rule, entirely overlooked by a soil survey, how- 

 ever carefully done. Thus the present soil maps do not distinguish 

 between the black oak, the sassafras, and the beech-red maple asso- 

 ciation areas. They are classed together as sand on the soil map. Very 

 numerous other instances might be mentioned. 



The forest associations may be arranged in the following order: (1) 

 Black Oak, (2) Sassafras, Birch, (3) Hickory, (4) Hard Maple, (5) 

 Beech, (6) Silver Maple, (7) Sycamore. This gives us a gradient scale 

 of forest associations that may serve to indicate the degree of soil 

 fertility, being too dry at one extreme for successful agriculture, and 

 too wet at the other. The optimum conditions for most crops occur in 

 the maple-beech portions. 



The several associations covering most of tlie old lake basin area are 

 believed to be stages of forest development tending toward the hard 

 maple-beech association as a climax. But the change is and has been 

 exceedingly slow, due to the correspondingly slow topographic changes 

 occurring on this area. So slow are the topographic and soil changes 

 occurring naturally on this area that the forest lias been become arrested 

 in its development and the several associations represent the arrested 

 stages, the succession of which will be published in the more complete 

 account. 



Yale University. 



