1899] DUNE FLORAS OF LAKE MICHIGAN I7I 
All of the species discussed up to this time are herbs, passing 
the winter near the surface of the soil or underneath it. The 
exposure to which shrubs and trees are subjected during the 
winter is so severe on the upper beach that few of the many dune 
species have representatives there. The individual shrubs which 
brave these conditions are relatively scattered, while the plant 
body is stunted and bears signs of the severe environment pro- 
vided by the beach. Much the commonest shrub, and the only 
one which occurs throughout, is Prunus pumila, the sand cherry. 
Poplars occasionally occur, Populus Lifer dand Popu- 
lus balsamifera (both the type and var. candicans) northward ; so 
too, the willows, Salix glaucophylla, adenophylla, and longifolia. 
The most striking feature of the plant life on the upper 
beach is the difference in its development at different localities. 
Te luxuriant flora of the north is in marked contrast to the 
impoverished flora at the south end of the lake. The Dune Park 
ach, for example, is tenanted only by Artemisia, Cnicus, Cori- 
pemmum, and a few scattering plants of other species. Anupper 
Peach on North Manitou island showed a great abundance of 
Elymus, Artemisia, Lathyrus, Genothera, and Populus balsamifera, 
Seehes with thirty-four other species which were rare to fre- 
oe Among these other species several are of considerable 
Beive: ; sid multifida, which also occurs on the beach at 
io and on several fossil beaches; Prenanthes alba, 
the beach: ah and thickets but seemingly out of place on 
On Similay guisetum hyemale, which sbi almost anywhere. 
arvense, two — e Empire, Achillea Millefolium and Equisetum 
MSc abc ants which never grow on the beach farther sours 
the former é eet Arabis ‘rata and Polygonum INOSESER (? ) 
on an ~ Sealing on the inland oak dunes about Chicago, occur 
The reasons age beach at the north end of Beaver island. 
hes are n : = great luxuriance of the northern upper 
greater . Bows It has been previously stated that the 
ance of driftwood on the more northern beaches 
May furnj ; 
2 = “onsiderable protection. This cause seems hardly 
olygonum with six stamens, very different from the type. 
