40 THE BOTANICAL MAGAZINE. [yoi. xxv. no. 2s9. 



II. Plant Associations. 

 Round the central association of submerged plants [Pota- 

 mogeton), there occur four concentric zones of marsh plants in 

 the basin of the swamp. Now I will give an account of the 

 distinctions of these five zones. 



1. Zone of Potamogeton. 



This zone extends through all the central part of the swamp 

 of the depth of 1.6-2m. Owing to strong winds and waves 

 which prevail in this zone of the swamp swimming hydrophytes 

 can not develop well, and heloph^-tes also can not proceed into 

 such a deep basin. Being favorable to epharmony/^ the 



submerged plants among which Potamogeton prevails, \\i\\ 

 flourish in this zone as the competitor of all, in such a large 

 quantity that they often check the boatin':j. This zone pro- 

 ceeds further landward through brooks and brooklets. As 

 the plants of this zone we count the following : — 



Chara sp., Nittlla sp., "' Vallisneria spiralis L., * Potamoge- 

 ton Gaudichaudi CuAM., " P. polvgonifolius Pour., * P. natans 

 L., ■" P. lucens L. var. teganumensis AIakixo., ^ P. crispus L., 

 * P. pcr/oliatiis L., P. serrulatus Rkg. ct Maack., "P. Midu- 

 hikimo Making, " Myriophyllum spicatum L., ^' Hydrilla ver- 

 ticillata Royle var. Roxburgii Casp., Ceratophyllum demersum 

 L., Najas major All., A^. minor All., N. graminea Del. 



The plants marked with an asterix are found abundantly 

 and used by farmers as a manure for their fields. Here it is 

 a noticeable fact that deep submerged leaves of Potamogeton 

 natans and P. lucens var. teganumensis are linear while upper 

 leaves are lanceolate. 



2. Zone of Zizania aquatica L. 



This zone proceeds as the innermost association of the littoral 

 flora and occupies the place of about l.Tni deep in average. 

 In this zone the conditions (as to wave and depth) of vegetation 

 are not sufficient to give a more favorable place for swimming 

 hydrophytes and helophytes, so that they can not flourish so 



1) Warming, 1. c. p. 2. 



2) The Bol. Magaz. Tokyo, Vol. XIX p. 142. 



