15] VEGETATIONAL TYPES OF FRESH WATERS 493 



is a zone of shallow water, not fluctuating significantly in level, and 

 bordered on its shoreward side by larger attached plants with leaves 

 reaching the surface, (c) The infralittoral, which is a deeper region. 

 Beyond this lies {d) the profundal, in which the light is insufficient 

 for photosynthesis, the only plants normally present being parasitic, 

 saprophytic, or chemosynthetic. Such a sequence is indicated in 

 Fig. 167, though it should be remembered that authorities often 

 diflter as to categorization and terminology. 



Eulittoral Cliff U<^ ^ ^ 

 (of fluctuating'TL^ ^ 



water) ~"-^ j |! (f ,i ,. , , . 



hrosional terrace ^"^Ssr 



Sublittoral terrace 



Profunda I 



Central plain 



Fig. 167. — Diagrammatic representation of a typical lake-marginal profile. The 

 limit of at all large benthic plants is commonly about the bottom of the sublittoral. 



In the shore-terrace and other shallow parts of the littoral, where 

 the bulk and activity of vascular plants and Mosses make serai 

 advance often quite rapid, there are usually abundant associated 

 Algae belonging to the benthos. The higher plants are, so to speak, 

 fugitives from land, the lower ones being ' true children of the water '. 

 But the higher plants themselves often constitute an important part 

 of the habitat of the aquatic microflora and microfauna and of any 

 larger Algae that may be present. Besides firmly attached benthic 

 types, the Algae include ones that are loose-lying (or in some cases 

 crawling) on the bottom or, particularly, among dense higher vege- 

 tation. Unlike the situation with higher plants and parasites, the 

 organs of attachment of these lower benthic plants do not normally 



R 



