CHAP. Lxx DISTRIBUTION 269 



have not been adequately investigated. To classify these other types 

 of psammophilous vegetation is impossible at present. 



Europe. There is considerable floristic agreement in the floras of 

 the coasts of northern Europe. Dunes of similar floristic character also 

 occur in Arctic regions, for instance in the east of Greenland, in Iceland,^ 

 and on the White Sea ; ^ but Psamma is absent, and is replaced by 

 Elymus arenarius, Juncaceae, and other species. 



Similar types of vegetation also occur at a distance from the coast, 

 for instance in the interior of North Gerviany. The production of dune 

 m Denmark and Germany takes place in heather-districts and on the 

 coasts, where strong winds are hostile to tree-growth. 



Borbas and Kerner ^ have described the similar vegetation of the 

 sandy soil of the Hungarian plains. Here, in accordance with the loose 

 texture of the soil, one finds the same long roots and rhizomes, metres in 

 length (for instance in Festuca vaginata, which here plays the part of 

 the sea-marram), and the same defence against transpiration ; tuberous 

 subterranean organs are also alleged to occur here. Adamovicz '^ has 

 given a description of dunes in Servia. Here the first colonists are the 

 annual Polygonum arenarium and Veronica triphyUos ; which are suc- 

 ceeded by Medicago minima, species of Bromus, Viola tricolor, and 

 others ; subsequently biennial and perennial rosette-herbs are found. 

 In the second year the plants to appear are all perennials, and various 

 associations (Festuca-association, Euphorbia-association, and others) 

 develop. The sand-dune may pass over into sand-puszta. 



Lacustral dunes in Switzerland exhibiting various types of oecological 

 adaptation have been described by Chodat.-'' 



The dunes along the French Mediterranean coasts are low and insignifi- 

 cant, and include as sand-fixing grasses Psamma arenaria, Cynodon 

 Dactylon, and others. On old dunes the flora differs from that of northern 

 dunes in being much richer in species, and apparently in including more 

 numerous grey-haired species. On the delta of the Rhone the dunes are 

 clothed with nearly impenetrable scented maqui, whose bushes include 

 Juniperus phoenicea (which attains a height of 6-8 metres), Pistacia 

 Lentiscus, Phillyrea angustifoha, Tamarix galhca, and Ruscus aculeatus.*^ 

 On old dunes forests of Pinus often appear. 



Africa. In Africa vast tracts of sand occur both on the coast and 

 in the interior. True shifting sand-dunes are encountered in the Sahara," 

 and thence as far as Syria. The vegetation is exposed by day to the 

 most scorching heat, and by night to a considerable degree of cold. Here 

 the dry season is very prolonged and the \'egetative season short ; and 

 the plants must be fitted to withstand the former, and utihze the latter.** 

 Among characteristic plants may be mentioned the grass Aristida pungens, 

 the polygonaceous Calligonum comosum, Herniaria fruticosa, Ephedra 

 alata, species of Limoniastrum, and others, of which some reappear on 

 sandy deserts in Asia.^ Kotschy describes the vast brownish-yellow 

 expanse of sand stretching east of Suez ; here the dunes owe their origin 



' H. Jonsson, 1905. ' Pohle, 1903. * Kerner, 1863. 



Adamovicz, 1904. " Chodat, 1902. 



Flahault, 1893 5 Flahault et Combrcs, 1894. 



^ For illustration see Schirmcr, 1893; ^lassart, 1898; Flahault, 19066. 



Seep. 275. ' Massart, 1898a. 



