FEB. 1911.] NAKANO.— THE VEGETAT. OF LAKES AND SWAMPS. 45 



of about 100m. The width increases often to five times in 

 the eastern part of the swamp, bnt it becomes sometime very 

 narrow by artificial works. 



5. Zone of Sagittaria sagittUolia. 



The zone is met with in the shallow pools, brooklets, and 

 the rice fields in the surrounding of the swamp. We may 

 point out the following plants as the inhabitants of this 

 zone :— 



Blyxa caulescens Max., Ottelia alismoides Perb., Sagittalia 

 sagittifolia L., Alisma plantago L. var. angasti folium Kunth , 

 Caldesia parnassifolia Parl., Sagittalia pygmsea Mio., Glyceria 

 acutiBora Tor., Leersia hexandra Sw., Eleocharis plantaginea 

 R. Br., Scirpus mucronatus L., Sc. triqueter L., Sc. lineolatus 

 F. S. Acoras calamus L., Eriocaulon sieboldianum Steud., 

 Aneilema Keisak Hassk., Juncus prismatocarpus var. Leschen- 

 aulti P. BuCH., Sub var. pluritubulosus Presl., Monochoria 

 korsakowii Reg. et Maack., M. vaginalis Pr. var. plantagi- 

 nea SoLMS.— Laub., Polygonum hydropiper L. var. vulgare 

 Meisn., Ranunculus sceleratus L., Rotala mexicana Ch., 

 Myriophyllum ussuriense Max., Nuphar japonic a D.C., Oenanthe 

 stolonifera B.C., Ambulia sessiEora Koch., Marsilia quadri- 

 foliata L. 



Besides these, we find here floating plants as :— 



AzoUa pinnata R. Br. var. Africana Bak., Salvinia natans 

 HoFF., Lemna major Griff., Lemna paucicostata Hegel. 



Here also occurs the vigorous growth of Potamogeton 

 polygonifolius. Of these plants, the peculiar aspect of the 

 vegetion of Sagittaria sagittifolia attracts our attention most 

 remarkably, hence the zone is so named. 



Now I will explain the inhabitats of five zones with 

 schematical figures. As a representative of each zone let us 

 take a characteristic plant. The number of individuals is 



represented with dots. 



