256 J. O. HAGSTEOM, CRITICAL EESEARCHES ON THE POTAMOGETONS. 



increases more conspicuously upwards, to the middle of the leaf, we have 7 oblongus 

 Spenner (P ohlongifolius DuM.). — Here may also be ranked f. macrophyllus Blytt 

 (specimens seen from Modum, Nonvay, 55, Blytt, hb. Uppsal.), f microphylhis 

 Baagoe, f. imbecillus Tis., f. prolixus Hagstr., f. pseudo-densus Asch. & Gr. Also 

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

 Vener and Lake Maelar, Sweden) and rivers I have found a very large-leaved form: 

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

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

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

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

 ition-forms are seen now and then. 



V. rotiindifoliiis Wallr. 



Hereto belonging forms are: f. caudiformis AscH. & Gr., probably also f. densi- 

 folius Meyer, 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. gracilis Ch. & Schl. (var. S. Mert. & K., p cordato-lanceolatus Fieb., 

 Y ovato-lanceolatus Reichb.): — »Foliis latioribus aut angustioribus 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 p gracilis Fr. gathered 

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

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

 F. lanceolatus Bl., according to Bly^tt's own specimens (hb. Uppsal.) has a stem- 

 leaf-size of 70—75x12 mm. The Friesian specimens, of Scania, gathered in 1824 

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

 elongate. 



Var. inandSClllirieilSiS Benn. The fruit is said to be » decidedly winged*. If 

 that means that the lid of the fruit is otherwise shaped than in P. perjoliaius, or 

 that the epicarp behaves as in P. prcelongus we shall here have quite a new spe- 

 cies belonging to either of the two preceding groups {Luc, resp. Prml.), according as 

 the leaf-margin be smooth or denticulate etc. But the fruit is perhaps winged in 

 dry state only, in which case the fruit may rather be called falsely keeled. I have 

 seen no specimens. 



P. pei'foliatllS v. laciistris Wallman in Liljebl., Utkast t. en sv. fl. 1816, 

 p. 706, is P. prcelongus Wulfen, which is now for the first time recorded as a Swed- 



