io NOTES AND COMMENTS [july 



was discussed in the last volume of Natural Science, had dictionaries 

 sent, if not hurled, at him, we think that he was right — for this is an 

 age of compromise — in sticking to kainogenesis, and he seems to have 

 Gegenbaur and other great authorities on his side. But to those who 

 believe that kainogenesis is a term for an empty conception, the reading 

 cenogenesis will doubtless seem preferable, for the German lexicon states 

 that tcevos means (1) leer, (2) vergebens, (3) eitel, (4) miissig, (5) aus- 

 geleert. But, after all, the gist of the matter is rather that we should 

 be sure that there is such a distinction as that between kainogenetic 

 and palingenetic, before we become excited in regard to our spelling of it. 



Flora of Sand Dunes. 



The flora of sand dunes has always been of great interest to botanists 

 from the number of peculiar species which it offers, and also — especi- 

 ally more recently — from its remarkable oecological importance. The 

 climatic and soil conditions under which it exists are so extreme in 

 character, and vary so continually, that it offers a suitable field for the 

 study of many problems dealing with the interaction of plants and 

 their environment. Partly from this reason, and partly because of the 

 absence of any complete study of dunes beside fresh water, Dr. H. C. 

 Cowles of Chicago University has just published (Bot. Gaz. xxvii. 1899, 

 Feb. to May, Fig. 26) an elaborate account of the general relation- 

 ships of the dune vegetation of the shores of Lake Michigan. This 

 paper is the first of a series on the subject, and treats of the geogra- 

 phical aspect. The extent of the whole area considered is great, but 

 most attention is paid to the south-east coast of the lake, where the 

 dune formation attains its maximum development — being largely due 

 to the action of north-west winds. 



In comparing those dunes to these familiar to observers in Europe 

 the resemblances are much more conspicuous than the differences. It 

 is remarkable how well many of the descriptions might be applied to 

 the dunes around the British coast, if only the names of the species of 

 plants were replaced by those of their European equivalents. Thus on 

 the beach, where we should find CaJrile maritima, Dr. Cowles records C. 

 americana. On the loose dunes of both continents Ammophila 

 arundinacca is the dominant and most important sand-binding grass. 

 The plant associations in both cases include those of the xerophytic 

 ridges, the intermediate swamps, and the mesophytic woods. In this 

 country Salix repens fringes the travelling dune, in Michigan it is 

 replaced by S. glaucophylla and S. adenophylla ; here Pinus sylvestris 

 and Bctula alba are the dominant trees on the fixed dunes, there it 

 is Pinus banlisiana, Betida papyrifera, Thuya occidentalis, Fraxinus 

 americana, etc. Many of the observations made by Dr. Cowles with 



