ZONATION ABOUT A POND 477 



454. Zonation in Fig. 366. The diagram represents some of 

 the principal associations observed in and about a rather shallow 

 pond in eastern Massachusetts in October, 1905. 



The pond was almost encircled by six zones of vegetation, 

 only one of which (the bog zone) entirely surrounded the water. 

 All the zones except that of the meadow consisted of wild spe- 

 cies, growing under nearly natural conditions. 



The pond itself had a rather scanty algal vegetation, among 

 which the most noticeable forms were a green alga (Bulbochcete), 

 related to (Edogonium, and a blue-green alga (Ccelosphcerium). 



Seed plants were well represented in the waters of the pond. 

 In the deepest portion, at J, no seed plants were found extend- 

 ing to the surface, but there were many young specimens of a 

 rush (Juncus militaris) with filiform leaves deeply submerged. In 

 general the pond was populated by pond lilies (Castalia), cow 

 lilies (NympJicea), three or more species of pondweed (Potamoge- 

 tori), with much pipewort (Eriocaulori) and duckweed (Lemna). 

 In the shallowest portions, usually in six inches or less of water, 

 were found some six other herbaceous species. 



The spermatophytic vegetation of the pond may be divided 

 according to its mode of growth into classes as follows : 



Floating plants Lemna 



Plants which grow rooted and submerged . . Potamogeton 



' Juncus 



Plants which grow rooted, but with more or less 



of the stem or leaf surface in air. 



Pontederia 

 Castalia 



NympJicea 



Plants of shallow water ("six inches or less), or f . 



v ,,.,,,. Eleochans 



which grow on floating raits like that at a, -i. ,, . 



with most of the plant body aerial . . . . [ 



455. Contents of the zones. It would involve too much 

 detail to enumerate the species of the several land zones 

 (II- VI), but they may be briefly summarized as follows : 



The bog zone contained some twenty-one conspicuous species, 

 especially peat moss and herbaceous seed plants. 



