J^g2 I'l.AXT STUDIES 



132. Societies. — Consjiieuous finiong hydrophyte societies 

 may 1)0 nientioiied the following: (1) Free-swimming soci- 

 eties, in which the j:)lants are entirely sustained by water, 

 and are free to move either by locomotion or by water cur- 

 rents. Here Ijclong the " plankton societies," consisting 

 of minute plants and animals invisible to the naked eye, 

 conspicuous among the plants being the diatoms ; also the 

 "pond societies," composed of alga?, duckweeds, etc., which 

 float in stagnant or slow-moving waters. 



(2) Pondweed societies, in wliicli the plants are an- 

 chored, but their bodies are submerged or floating. Here 

 belong the " rock societies," consisting of plants anchored 

 to some firm support under water, the most conspicuous 

 forms being the numerous fresh-water and marine algiv, 

 among which there are often elaborate systems of holdfasts 

 and floats. The " loose-soil societies " are distinguished 

 by imbedding their roots or root-like processes in the 

 mucky soil of tlie bottom (Fig. Hi:!). The water lilies with 

 their broad floating leaves, the pondweeds or pickerel weeds 

 with their narrow submerged leaves, are conspicuous illus- 

 trations, associated with which are alga;, mosses, water 

 ferns, etc. 



(3) Swamp societies, in wliich the plants are rooted in 

 water, or in soil rich in winter, but the leaf -bearing stems 

 rise above the surfa.ce. The conspicuous swamp societies 

 are "reed swamps," characterized by bulrushes, cat-tails 

 and reed-grasses (Figs. 1G4, 107), tall wand-like ^louocoty- 

 ledons, usually forming a fringe about the shallow margins 

 of small lak(.'s and ponds; "swamp-moors," the ordinary 

 swamps, marshes, l)ogs, etc., and dominated l)v coarse 

 sedges and grasses (Fig. lO:)); " swa.mp-tliickets," consist- 

 ing of willows, alders, bii'ches, etc.; "sphagnum-moors." in 

 which sphagnuui moss iire<lominates. and is a<M'ompanied by 

 numerous peculiar orchids, lu^aths, carnivoi-ous ])huits, etc. ; 

 "swamp-Forests," wliich arc largely coniferous, tamarack 

 (la,ri'h), jiine, hemlock, etc., ])revailing. 



