228 HALOPHYTES SECT, vn 



herbs, whose frequently prostrate shoots stretch loosely over the sand 

 on all sides, many of them without striking root : this is true, not only 

 of Ipomoea Pes-caprae, but also of the East Indian Euphorbia thymi- 

 folia, E. pilulifera, species of Sida, Indigofera enneaphylla, 1 also of the 

 American Euphorbia buxifolia, Heliotropium inundatum, Cakile aequalis, 

 Portulaca pilosa, and others. All these are small-leaved and more or 

 less fleshy. 



It is difficult to draw a distinction between the true halophytic 

 vegetation of the sea-shore, and the xerophytic vegetation of dry, warm, 

 non-saline sand, which borders on the shore or occurs in inland dunes ; 

 such a delimitation must be left to the future. 



ft. Shingle-banks. 



In another direction the sea-shore is not sharply delimited, at least 

 in parts of the Earth where the Ice Age has left numbers of erratic blocks 

 scattered on the beach ; in such cases the vegetation of the sandy beach 

 merges with that of rocks, or a combined vegetation representing sand 

 and rock arises, though with characteristics appertaining to the latter. 2 

 A shingle-bank may also arise by weathering of the shore-rocks and the 

 rounding-off of fragments by the action of waves. See also Chapter LXII. 



c. Halophilous Forest and Bushland on Sand. 



The vegetation on sandy sea-shore is frequently succeeded on the 

 landward side by forest and bushland, which also appear inland on saline 

 sand. But there is always a question as to whether this formation 

 must be regarded as halophilous or as psammophilous : and this question 

 Kearney 3 has propounded in reference to dune-plants in North America. 

 Tentatively I regard the undermentioned types as halophilous. But in 

 any case the distinction is of subordinate import. Psammophytes and 

 halophytes intermingle on sandy shores near the sea. Towards land 

 the vegetation gradually becomes purely psammophilous, in proportion 

 as the salt is washed out of the sand ; nevertheless the undermentioned 

 low littoral forests and bushlands on flat coasts are halophilous, since 

 they occur only on sea-coasts, and their roots probably extend down to 

 saline water permanently present in the soil. 



Barringtonia-association. As the first of these may be mentioned one 

 in Eastern Asia and Australia described by Schimper 4 the Barringtonia- 

 association in which a part is played by the large-leaved, large-flowered 

 myrtaceous Barringtonia racemosa and other species, also by Hibiscus 

 tiliaceus, Casuarina, Thespesia populnea, Terminalia Catappa, Heritiera 

 litoralis, and others. The trees in Barringtonia-forest are short, have 

 curved trunks and branches, and large leaves that are leathery or xero- 

 phytic in some other way. The forest may be rendered wellnigh impene- 

 trable by Caesalpinia Bonducella, species of Canavalia, and other lianes. 

 In Eastern Asiatic littoral forests there may occur coco-nut palms, cycads, 

 casuarinas with their Equisetum-like aphyllous switch-shoots, and 

 peculiar types of Pandanus, including P. labyrinthicus and P. odora- 



1 Schimper, 1891. 



* '.Mixed vegetation', see p. 143 ; for figures and details, see Warming, 1906. 



* Kearney, 1904. Schimper, 1891. 



