50 J. O. HAGSTRÖM, CRITICAL RESEARCHES ON THE POTAMOGETONS. 



Var. diffusus has in general rather long leaves. This form, however, shows 

 that sometimes short-leaved specimens also oecur. It is gathered by Dr. G. Tiselius 

 at Ulva near Uppsala 1866 (hb. Stockholm.) and at Björkby (Uppsala), 66, Ahr- 

 ling (hb. Uppsal.). A similar plant is observed at Jonsberg (Ostrogothia), 80 (hb. 

 Uppsal., Lund.) and »in Flusse Bystrzyen», Poland 84 (hb. Lund.). — It may be 

 considered a parallel-form of var. ungulatus i. acerosus. 



Var. nioilgolicus Ar. Bennett. 



Notes on Potamogeton in the Journ. of Bot. 1894, 203—204: — Caidis capilla- 

 ceus; folia löete viridia setacea uninervia; pedunculus longissimus (ad 250 mm); spica 

 brevis triverticillata ; microcarpus. Ex A. Benn. et specim. Przewalski. — Fig. 16, //. 



This variety comes nearest to v. diffusus f. laxus or glaucescens by the capilla- 

 ceous stem and leaves, the apex of which is also like that of var. diffusus, but dif- 

 fers by the lighter green colour, one-nerved leaves without hypoderma, long pedunc- 

 les and small spikes. One could almost consider it to be a separate species, but 

 further researches are required for full certainty. The plant originates from Asta, 

 Mongolia occ., where it is collected by N. M. Przewalski in 1871 (hb. Stockholm.). 

 True P. pectinatus is gathered in Mongolia media 1886 by Potanin (hb. Stockholm.), 

 also this microcarp. 



Var. zosteraceus (Fr.). 



P. zosteraceus Fries, Nov. Fl. suec. 1828, 51. — P. pectinatus f. zosteraceus 

 (Fr.) Almquist in Hartman's Handb. Skand. Fl. 1889, 56. — P. pectinatus var? 

 latifolius Robbins, Bot. King's Expedition, 1871, 338 ex Morong, Najadacere 1893, 

 t. LIX: — Caulis internodiis elongatis. Folia caulina inferiora et superiora lata 

 (resp. ca. 3 et 2 mm), 3( — 5)-nervia obtusiuscula emu mucrone, våghus laxis brevi- 

 bus, 15—20 (25) mm. Pedunculi longissimi. — Sec. cl. Auct. et specimina Hart- 

 maniana. 



The typical Hartmanian specimens from Utön, »in extimis Sudermannia» mari- 

 timis» (hb. Uppsal.) is a deep-water form with few branches developed in the upper 

 part of the stem. The leaves are comparatively broad as well in the upper part of 

 the stem, and their sheaths are obviously broad, short, and enlarged, and with 

 thin, broad, grayish, membranous margins. Its habitat seems to be in the 

 northern part of the Baltic. But also the N. American plant from Nevada and 

 California may be congruent with our Baltic plant judging from the drawing of it 

 made by Rev. Tu. Morong in lus NajadaoetB. On the other hand the German spc- 

 « limens, v. zosteraceus Casp., v. flitriatilis SoHttBL., v. liixuriaits DÖLL, are vciy liUely 

 not identio with the plant here spöken of, but to be referred bo f. interruptus or to 

 f. dichotomu8. 



