ae a 
EE EEE a a a a i 
NS ost ree = — a 
1899] DUNE FLORAS OF LAKE MICHIGAN 371 
heath into a forest is illustrated by figs. 2gand 25. Ineach case 
the heath is encroaching on a beach and is being followed up 
fan passu by the forest. The advance of the heath is secured 
mainly by vegetative propagation, that of the forest by germi- 
tation of seeds. This fact, together with the need for protection 
to the seedlings, prevents the forest from overtaking the heath in 
the struggle for more territory. So far as observed, the heath 
always precedes the forest, when the latter is developed in an 
exposed situation. 
In the region as a whole, the pines are by all odds the char- 
acter trees of the coniferous forests, and especially the white 
pine, Pinus Strobus. This tree is found at all places along the 
*oast. At the south end of the lake the scrub pine, Pinus Bank- 
ana, is more abundant than the white pine, while at the north 
end the red pine, Pinus resinosa, is often as frequent as the white 
pine. The distribution of the pines is very surprising. The 
‘cub pine is the most northern of the three pines mentioned, 
‘nd its farthest known southern limit is about the south end of 
Lake Michigan. Peculiarly enough, it is far more abundant than 
all other Conifers put together at the south end of the lake, 
While it is much less abundant to the north along the lake shore. 
Was not seen at all north of Glen Haven, though it is reported 
fon inland. The red and white pines have in general a 
‘ea Southern range than the scrub pine, and yet they are 
sds abundant northward along the lake than is the latter. 
aihermore, these pines become more abundant absolutely 
i 8°es northward. The red pine was not seen south of 
‘ntwater, 
North of Grand Haven 7huya occidentalis becomes a frequent 
Ee ot the coniferous forests - sometimes it becomes as domi- 
C as the Pines. The same may be said of Abies — 
is = ‘EWas not seen south of Frankfort. Juniperus dice 
oo” €speciaily southward. With the aii 
_ deciduous trees, especially at protected see e Lee 
"erg ee are Betula papyrifera, Tilia Americana, op 
‘ Ostrya Varin: 
