14G 
FIFTEENTH REPORT. 
On the third hill the pines are reduced to scattered individuals in 
a dense growth of deciduous trees. This hill is less steep and there 
is no caving of the hillsides. The deciduous trees are well-established 
ami have accumulated a noticeable amount of humus. At the edge 
of the river there is a marshy strip about ten feet wide. The differences 
in soil and moisture conditions are also seen in the flora. The follow- 
ing plants occur here: 
Pinus strobus 
•T u n i peril s v i rgin i a n a 
Smilax hispida 
Carya ovata 
Cory 1 us americana 
Ostrya Virginian a 
Fagus grandifolia 
Quercus alba 
Quercus rubra 
Quercus velutina 
Anemone cylindrica 
Hamaraelis Virginian a 
Rosa sp. 
Rhus glabra 
Yitis sp. 
Cornus stolonifera 
Cliimaphila umbellata 
Prunella vulgaris 
Gerardia grandifolia 
Rudbeckia liirta 
Helianthus sp. 
Besides the above, Alnus incana occurs with Cornus along the marshy 
shore. 
The fourth and fifth hills have no pines left, their former presence 
being attested only by the large slumps which remain from the lumber- 
ing of the past. A sharp ravine separates these hills to quite a dis- 
tance from the river. The ground here is wet, almost swampy, and 
hence springs the small brook which has cut the ravine. The ordinary 
oak and hickory of the riverward face of the hills is here varied by 
the admixture of a little burr-oak and white ash and quite a lot of 
. red maple. In and bordering this wetter ground are three plants of 
special significance: Epigaea repens, Gaultheria procumbens, and Vac- 
einium canadense. These three plants, especially Epigaea, can always 
be taken as signs of the pine association in this region, even when the 
pines have left no signs of themselves. Gaultheria and Vaccinium 
are too easily bird-distributed to be safe criteria of themselves, but 
when associated with Epigaea they may be always so regarded. 
From the preceding it is seen that pines are at present quite scarce 
on these hills, persisting on but a few of them, and then only on the 
sides toward the river. They have been left here on the more inac- 
cessible places by the lumbermen, and have persisted because the de- 
ciduous trees can not use the sterile and rather unstable soil where 
they are perched. The deciduous trees do not seem as well able to 
stand ihe caving of the soil as do the younger pines, nor do they es- 
tablish themselves as well on the denuded areas. The pines are -not 
reproducing themselves to any extent; no cones were present on the 
trees, and only one fallen cone was found. These pines may fruit 
only at long intervals, most of them are too young to fruit. With a 
fair seed-production the pines might persist here for a long time, but 
seed-production has been nearly entirely stopped, probably because of 
the death of the older trees where the soil has caved from about their 
roots. 
University of Michigan, April, 1013. 
