274 BOTANICAL GAZETTE [ocroBER 
it is abundantly represented in the vicinity. A variety of hickories 
is found, most common of which are Hicoria ovata, H. alba, H. 
odorata, and H. glabra. ‘These are associated with Quercus rubra, 
and Q. alba is present. 
The other vegetation also shows a number of easily recognized 
characteristics. The proportion of leguminous species (Melilotus, 
Trifolium, Vicia) is high; composites (Aster /aevis and other summer- 
blooming species) are frequent; Podophyllum peltatum, Erythronium, 
Muhlenbergia diffusa, Scrophularia marylandica, and Cornus candi- 
dissima are common species. Counting in the smaller vegetation, 
the society is not rich in species, but is rich in southern forms. 
(2) Black oak society.—The cemetery bluff conditions, brought 
about partly by the porous sand and partly by slope, are much more 
arid than the till bluffs. The hickories and red oak disappear from 
the forest, and Quercus velutina becomes most common, 53 per cent. 
of the individuals on the slope above the 760-foot contour line being 
black oaks. Quercus alba is common, and in places west of Ann 
Arbor Q. imbricaria. 
Comparing the other vegetation with that of the oak-hickory 
society, it is found that equal differences exist. The May apple 1s 
rarely found; there are fewer leguminous species; ericaceous shrubs 
are common; and the proportion of composites is high. The er 
tation is rich in species, characteristic of which are Lespedeza capitala, 
_ L. violacea, Solidago caesia, S. speciosa, S. nemoralis, S. rigida, 
Gaultheria procumbens, Gaylussacia resinosa, Vaccinium vacillans, 
Angelica villosa, Viola pedata, Lupinus perennis. 
All of the numerous species of grass which clothe the steepét 
slopes have prominent adaptations serving to bind down: and 
the soil from outwash. They are all perennials, have deep root 
systems, strong woody stems and rhizomes, and grow in ee 
tufts which offer the greatest resistance both to being torn apart an 
to being displaced. Even loose sand, which otherwise would i 
quickly washed away, is by this means held in place indefinitely, 2” 
the steepness of slope so formed is often surprisingly great. ae 
found that the angle of repose of the dry sand composing the 
Was 28° 35’. The mean angle of the slope was 39° 55/3 the @ ae 
slope of the bluff as held by the soil binders is 11° 20’ steepe! 
