22 6 HALOPHYTES SECT, vn 



Europe, Cakile maritima, Salsola Kali, and species of Atriplex, which 

 always find the open space they require, and are not prevented from 

 developing by the shifting nature of the soil. In addition, perennial herbs 

 with creeping rhizomes occur, as they accord with the often unsettled or 

 shifting, loose soil, and easily maintain their position when once firmly 

 rooted : among such species are Honckenya peploides and Triticum 

 junceum. Only on less disturbed, and particularly on stony soil, raised 

 slightly above the sea-level, does one encounter perennial species with 

 a multicipital, deep tap-root, such as is possessed by Mertensia maritima 

 and Crambe maritima. 



As the soil is now and again flooded by sea-water, and the water 

 in the soil lies at a slight depth below the surface and is strongly saline, 

 and furthermore as the soil is saturated with salt brought by sea-foam 

 and spray from the waves, the vegetation is definitely halophytic. Its 

 xerophytic and halophytic nature is revealed in a number of characters. 

 Fleshy leaves are possessed by most ; and a glaucous wax-coated epider- 

 mis shows itself in some types, such as Triticum, Eryngium, Crambe, 

 Mertensia, and Glaucium flavum. Hairs clothe Kochia hirsuta and 

 Senecio viscosus ; while thorns appear on Salsola. On certain spots 

 in this formation may be found the cactiform Salicornia herbacea, whose 

 home, apart from this, lies in salt water. All these plants are certainly 

 photophilous and incapable of enduring shade. 



The species often range themselves zonally into associations according 

 to stability of the soil and other relations (including humidity of soil). 

 In many places the succession, travelling from the sea landwards, is as 

 follows : 1 



1. Salicornietum, with S. herbacea. 



2. Atriplicetum, with many species of Atriplex, Suaeda maritima, 



and others. 



3. Cakiletum, with Cakile maritima, Salsola Kali, Honckenya, and 



Crambe maritima. 



4. Triticetum, with Triticum junceum, and others. 



The zones nearest the sea consist solely of annual species, but those 

 on the landward side also include perennial species belonging to the 

 growth-forms already mentioned. 



Farther south, for instance on the shores of Holland, one meets with 

 several other species, including Convolvulus Soldanella, which belongs 

 to plants possessing subterranean runners, and Euphorbia Paralias. 

 Still farther south, on the shores of France, yet other species, among 

 them Matthiola sinuata, appear : yet the growth-forms remain the same 

 and the formation the same. 



On the shores of other seas the same formation seems to reappear, 

 and to differ merely in flora. 2 



On the borders of fresh-water lakes the zonal distribution of vegetation is 

 similar, as are the growth-forms, in so far as they are dependent upon the loose 

 texture of fine-grained sand, and on the degree of repose to which the soil is subject. 

 But only a few observations have been made regarding the sandy shores of fresh- 

 water lakes. According to Cowles,* the ' lower beach ' is characterized by Sand- 

 Algae. The ' middle beach ', lying between the high-water marks of winter-storms 



1 Warming, 1906, 1907-09. 



* In regard to North America, see Harshberger, 1900, 1902. * Cowles, 1899. 



