1899] DUNE FLORAS OF LAKE MICHIGAN 193 
Perhaps the most tenacious of all the dune-holders on the coast 
of Lake Michigan is Calamagrostis longifolta. This grass, as has 
been seen, is not of first importance as a dune-builder, but when 
it has once built up a dune it seems almost impossible to dis- 
lodge it. At the left of the basswood tree in jig. 23, there is 
shown a clump of Calamagrostis directly facing the prevailing 
wind at the summit of a mound, and stubbornly holding its posi-| 
tion. The leaves, stems, and roots are all stiff and wiry, almost 
perfectly resisting the mechanical action of the wind. The roots 
in the sand form a network so dense that it is almost impossible 
for the wind to remove the sand from among them. 
From an economic standpoint, Ammmophila arundinacea is a 
more successful dune-holder than is Calamagrostis, but its greater 
Success is due to its extensive vegetative propagation. The 
dense social growths of Ammophila make it difficult for the 
wind to get a start in the process of sand removal, whereas the 
ee readily picked up from between the more scattered 
= Calamagrostis, An individual tuft of the latter, however, 
she i Be much more resistant~than a tuft of Ammophila. 
the a too, grows in more exposed situations than does 
‘a Ces and hence is a valuable dune-holder in places 
mophila might not thrive at all. 
ia erty dune-holder is Prunus pumila. A very 
covered ree ee fie upper beach is a truncated eone literally 
tangle of de am and sometimes on the sides with a dome 
has ea er of the sand cherry. — wind 
Wait until the , € sand which it can reach and is obliged to 
wind to blow ‘i ems and roots decay sufficiently to allow the 
iS one of es ae away and get at the sand beneath. Prunts 
Process of “og plants to succumb befor: the cane in the 
Short, but aoc Site perhaps its life cycle is normally 
steater and Saas ably the process of drawing up water a 
Up the une ¢r distance each year compels the plant to give 
qual strugo| 
Sooner or late 
are all removed “8 dead roots and stems of the dune-holders 
» and the wind becomes the undisputed master of 
