432 BOTANICAL GAZETTE [JUNE 
Michigan furnish fine illustrations of the ability of plants, and 
especially trees, to spread from an area where the conditions of 
growth are more favorable to one where they may be much less 
so. They emphasize the plasticity of plants. The species may suf- 
fer in vigor of growth and have a much less bulk, but they usually 
fruit very freely, often surprisingly so. At White lake was a 
basin filled with sand surrounded and underlaid by drift clay, or 
by materials that enter into the drift formation and on which in our 
latitude the mixed forests of deciduous species mainly occur. 
North of the lake, with its deeper and drier sand, the oaks were 
almost the only kinds to come in and compete with the white 
pine. South of the lake, where there was more dampness and a 
nearer approach of the glacial drift to the surface, except on the 
high dunes, and a more marked tendency to a loamy condition 
of soil, there were many more kinds of trees and herbaceous 
plants to share the ground with the pine. But the trees best 
adapted to a clayey soil not only crept across the area of low 
sand ridges and the intervening and more favorable hollows but 
passed up and appeared in force on the high dunes along the 
Lake Michigan shore, just as they may be seen on a narrow strip 
of dunes superposed on the clay of the lake shore, where a 
hardwood forest closely abuts it without any sand-filled basin to 
the eastward. 
I have been struck repeatedly by the distribution of some 
of the deciduous trees of dune regions, such as that at the head 
of Lake Michigan in Indiana and Illinois. The basswood is one 
of the best examples. .It appears eastward in the area of 
broken or active dunes where it is practically confined to a nar- 
row belt by the lake shore and toa similar belt further south 
along the Calumet river. It frequents the more protected slopes 
of dunes or hollows lying between neighboring sand_ hills, 
though like other trees, from the shifting character of this por- 
tion of the dune region, it may be so situated as to give the 
appearance of growing originally on a crest. West and south 
it appears again in the areaof low sand ridges and shallow lakes 
and ponds where the conditions are more like those of forest 
