FEB. 1911.] NAKANO.— THE VEGETAT. OF LAKES AND SWAMPS 5i 



3. Helophytes round submerged hydrophytes are arranged 

 clearly in four zones. As the ecological factors of this 

 arrangement were considered : — 



a. bathometric factor, b. hydrodynamic factor 

 c. Edaphic factor d. human interference. 



4. The vegetation of the eastern part of the swamp has an 

 appearance of a marsh (Sumpf ), and its plants, both in 

 species and individuals, are the richest of all. 



5. The flora of the swamp has the nearest alliance with that 

 of the Asiatic Continent, and has a closer affinity to the 

 floras of southern lands than to those of northern lands. 



6. The aquatic and marsh plants which I mentioned in the 

 present report are 49 species and 9 varieties. The nu- 

 merical relation of these two groups is as follows : — 



Hydrophytes = 29 Helophytes =29 



submerged 16 



swimming 8 



floating 5 



29~ 

 Namely, the ratio of the number of hydrophytes and helo- 

 phytes is 1. As the helophyte increases hand in hand with 

 the age of a lake, the ratio in young lakes must be larger than 

 one. 



From this point of view, Tega-swamp which is originated 

 from the course of the river, resembles a lake of old ages. But 

 the time must be long, before it becomes entirely marshy. 



Oct. 1910. Botanical Institute, 



Imp. Univ., Tokyo. 



