FLORA OF THE WHITE LAKE REGION 433 
strips or islands of the prairie region, where it is accompanied 
by such trees as Quercus bicolor, Q. rubra,and Q. acuminata, addi- 
tional to the common black oaks which are spread throughout 
the dune region. Other trees are the hackberry, white elm, 
tulip tree, shagbark and bitternut hickories, white ash, blue 
ash and some kinds of Crataegus. Most of these are common 
trees on the drift clay to the south and west, and all appear 
somewhere on the bordering clay-land forests, but are scarcely 
seen in the area of broken dunes, except an occasional red 
oak, some white oak and bur oak or a bushy form of the 
Celtis specifically distinct (C. pumila Pursh). Lying between 
these two sections is a strip where the basswood as well as these 
other trees is absent. There would seem to be sufficient moisture 
at least, for it is mostly a region of low sand dunes, parallel sand 
tidges, and intervening sloughs, the ridges with a prevailing heath 
vegetation. It is the home of the gray pine (Pinus divaricata) , 
Sometimes almost exclusively so. Where the white pine prevails 
or shares the ground more freely with the gray pine, the bass- 
wood comes in. This is a common tree of the forests to the east- 
ward of these dunes in the drift covered areas, together with the 
sugar maple, beech, tulip tree, and various other kinds, But nearly 
all except the basswood and the oaks cease in the belt of less 
pure sand or sandy loam, lying between the dunes proper and 
the clay region, There may be in the basswood peculiarities of 
Structure or physiological adaptations better fitting it for xero- 
phytic conditions than the others when they move away from such 
as are suited to mesophytes. Its leaves become much thicker than 
When growing in its usual home. There is in the fruit one 
advantage for more effectual dispersion, the ligulate bract 
attached to its peduncle, which in a strong wind helps to carry it 
to quite a distance from the parent tree. Most of the trees 
which formed the mixed forest to the south of White lake, and 
like the basswood showed this ability to spread 42. poms 
Contiguous region more congenial to them, not only fruit eed 
but have a heavy seed, which, when lying on the surface e a 
8round, is not easily displaced. Such seeds sprout quickly 
