XVI International Botanical Congess

The results of revision of species composition of taxonomically obscure Potamogetonaceae occuring on the northern coast of the Sea of Okhotsk and Upper Kolyma Rv. drainage are given. It is represented here by 16 species and subspecies: Potamogeton alpinus Balb., P. tenuifolius Rafin. (P. alpinus Balb. subsp.tenuifolius (Rafin.) Hult.), P. berchtoldii Fieb., P. pusillus L., P. borealis Rafin.(P. filiformis Pers. var. borealis (Rafin.) St.-John), P. natans L., P. pectinatus L., P. perfoliatus L., P. praelongus Wulf., P. sibiricus A. Benn., P. subsibiricus Hagstr. P. gramineus L. s.l. is extremely variable in our region, it includes P. gramineus L. s.str., P. graminifolius (Fries) Fryer, P. wolfgangii Kihlm. Nontypical samples of P. perfoliatus L. occur in some locations, which are close to P. richardsonii (A. Benn.) Rydb. (=? P. sachalinensis (Levl.) Levl.), but latter species on the Russian Far East needs further study. The information about occurence P. maackianus A. Benn. needs to be confirmed.