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



increases more conspicuously upwards, to the middle of the leaf, we have ? oblongus 

 Spenner (P oblongijolius Dum.). — Here may also be ranked f. macrophyllus Blytt 

 (specimens scen from Modum, Norway, 55, Blytt, hb. Uppsal.), f microphylhts 

 Baagöe, f. imbecillas Tis., f. prolixus Hagstr., f. pseudo-dcnsus Asch. & Gr. Also 

 v. Muelleri Bennett is likely to be reckoned here. — In great lakes (e. g. Lake 

 Vener and Lake Ma-lar, Sweden) and rivers I have found a verv large-leaved form : 

 f. pxornatus n. f. — Folia caulina maxima 80 — 150 X ±30 mm. — 

 A form with beautifully cuspidate leaves (sec fig. 117, A') is: 

 f. aentifolius n. f. — Folia caulina cuspidata. This form is gathered in Swe- 

 den Ostrogothia, Jonsberg, Gränsö, 77, by Elmquist (hb. Lund.), typical, but trans- 

 ition-forms are seen nou and then. 



V. rotnndifolins Wallr. 



Hereto belonging forms are: f. caudiformis Asch. & Gr., probably also f. doisi- 

 folius Meter, and others, all with rounded leaves (foliis rotundis: W.). A small- 

 leaved plant from India orientalis, hb. WiGHT (hb. Stockholm.) presents very short 

 peduncles, only 20—25 mm. 



Examples with comparatively narrow and long leaves are aggregated under 

 the name of » Forma gracilis» by CHAMISSO and Schl. This will consequently be- 

 come the third variety: 



V. graeilis Ch. & Schl. (var. 8. Mert. & K., p cordato-lanccolatvs Fieb., 

 Y ovalo-lanceolatus RErciiB.): — »Foliis latioribus aut augustioribus ex ovata basi 

 angustatis.» It is met with not only, as often stated, in current water, but also 



in smaller lakes. So is, for example the hereto belonging [3 gracilis Fr. gathered 

 in Ifö-Lake, Scania. Such forms, however, as f. longifoliua Tis., with the leaf-size 

 of 80— 100 X 15 — 18 mm may really be inhabitants of the greater and colder rivers. 

 V. lanceolatus Bl., according to Blytts own specimens (hb. Uppsal.) has a stem- 

 leaf-size of 70 — 75x12 mm. The Friesian specimens, of Scania, gathered in 1 SJ 1 

 (hb. Uppsal.) measure a leaf-size of only 50— 60x12 — 15 mm, thus not verv nuuh 

 elongäté. 



Var. inaiKlscliurioiisis Benn. The fruit is said to be »deoidedly winged». If 



that means that the lid of the fruit is othcruise shaped than in /'. perfoHatua, or 

 that the epiearp behavea as in l\ prcBlongus we shall here have quite a new spe- 

 ciea belonging to eithcr of the two preceding groups (Luv., resp. Prcel.), according as 

 bhe Leaf-margin be smooth or dentioulate etc. But i\\r fruil is perhapa winged in 

 dry state only, in which casc the fruit may rather I»*' called lalscly keeled. I have 

 scen no specimens. 



I*, perfoliatns v. lacuslris Wallmah in Liljebl., Utkast t. en sv. fl. 1810, 

 p. 700, is /'. prcelongus Wulfen, which is now for bhe firat time recorded as a Swed- 





