46 



C-O" Surrounding Valley 



0" Bank of the swamp 



0^ 



THE BOTANICAL MAGAZINE. 



[Vol. XXV. No. 



■ Sagittalia sagittifolia. 

 Phraginites communis. 

 Typha angustifolia |: 



Zizania aquatica ~ 



2" 

 Potamogeton rat;m?. ? 

























i---^^hxd 



=->.-., .. , 

















^^ - ^:- : 



















'-;"/-{^: 













__1 — L:! 





I- :V:"->f 



;^^>\ :^;-^--^.?r-\^:v 



Depth in Shakn (ca. ft ) 



These figures are obtained from the survey of the t\'plcal 

 vegetations of the swamp, as in Konoyama, Nenogami, Minowa, 

 etc. 



III. Ecological Factors. 



Upon considering all the facts above mentioned, we may 

 point out at least the following agencies as the ecological 

 factors here at work. 



a. bathometric factor b. hydrodynamic factor 



c. edaphic factor d. human interference 



a. Bathometric factor. 



The association of Zizania aquatica proceeds in the swamp 

 as the innermost pioneer of the littoral flora, while Phragmites 

 alwavs comes on the shore, and Typha with a dense growth ot 

 Zizania occurs betw^een them. On the contrary, the central 

 part of the swamp is a mere abode of submerged plants. In 

 this case, the supply of the water to the plant and the regu- 

 lation of transpiration, as Warming referred, ^^ seem directly to 

 evoke the arrangement of five zones, according to the rate 

 of adaptation to water. Therefore, the distinction of four 

 zones, Potamogeton-, Zizania-, Typha- and Phragmites- zone 

 would have probably come indirectly from the difterence of the 



1) I.e. p. 9G. 



