yp] DUNE FLORAS OF LAKE MICHIGAN 387 
the inland fresh-water area in the United States. The life con- 
ditions appear to be essentially alike on all dunes, whether marine 
or not, and there are found not only identical life habits, but 
wen identical plant species. 
Warming reports Chlamydomonas on the strand in the same 
lations as along Lake Michigan. Among the sand-binding 
plants, Warming and Graebner give an important place to mosses. 
Along the Lake Michigan dunes, mosses do not appear to any 
seat extent until establishment is nearly complete. On the 
Denmark coast, the Agropyrum dunes are lower than those 
formed by Ammophila, just as along Lake Michigan. The 
Danish dunes have also been studied by Raunkiaer, Paulsen, and 
Reilberg. Erikson has studied the similar dunes of southern 
Sweden, Giltay and Massart those of Holland and Belgium. 
The dunes on the islands along the German coast have been 
carefully studied by Buchenau and to some extent by Knuth. 
Sraebner, in his exhaustive work on the North German heath, 
lscussés the origin of the heath on naked dune sand. He gives 
“Important place to alga and moss protonema, since they 
Mecede other vegetation, forming the first humus and causing 
ie sand grains to cohere. It is doubtful if these lower plants 
“so important as sand-binders along Lake Michigan. Rothert 
md Klinge have studied the coast vegetation of Russia. 
a French dunes have been very carefully studied by oat 
= ia and sais in association with Combres. Some eh 
, een done in France by Constantin and Masclef. ; z ° 
ea in Spain and Portugal, covering a period of nearly 
m iS very complete and satisfactory. Daveau has worked 
Out eS 2 
hag “onditions along the coast of Portugal. On these more 
Mic ftes, the plant species resemble those along Lake 
0 less than do those in northern Europe, but the life 
HS are the same. : 
— dune flora of South Africa has been touched upon by 
alas Chile by Kurtz and Reiche, that of tes 
— Y Kjellman, that of New Zealand by Diels. The tropica 
" Indo-Malay sia have been studied in detail by Schimper, 
