62 J. O. HAGSTROM, CRITICAL RESEARCHES ON THE POTAMOGBTONS. 



Conspectus for mar inn: 



a. Serrulatus: — Folia serrulata, in margine iis P. perfoliati similia. 



f. cu-Cooperi Gbabbner, Potamog. in Engler, Pflanzenr. IV: 11, 1907, 134. — 

 P. undulatus var. Gooperi Fryer 1. c, tab. 313. 



Stem-leaves broad and elongated, usually 60—70 mm long by 20 — 30 mm in 

 width. A single station known: England, Leicestershire: Canal Loughborough. This 

 plant might possibly be P. crisp. X proel. 



f. Jacksonii (Lees). — P. perfoliatus var. Jacksoni Lees in The Bot. Record 

 Club Report 1880, 150. — P. undulatus {crispus X perfoliatus) var. Jacksoni (Lees) 

 Fryer, 1. c. 290—291: — Stem-leaves commonly of the size tI mm (45—60x13—20). 

 In habit often very like P. perfoliatiis L. 



Distribution. England, Chester, River Dee, 91, Billups (hb. Stockholm.), 

 Cambridgeshire, Parsonware Drove, Benwick, 92, Billups & Fryer (hb. Stockholm.). 



f. scoticus n. f. — Folia anguste ovato-lanceolata. — Stem-leaves norrower and 

 comparatively more elongated than in the precedent and following forms, 50 — 80 X 

 X 6—13 mm. 



Distribution. Scotland, Stirlingshire, Union Canal supra Falkirk, 94, Stirling 

 & KiDSTON (hb. Stockholm, et Lund.). 



p. Serratus: — Folia serrato-dentata. 



f. Fisclieri n. f. — Folia caulina ca. 20 — 25 mm longa, 10 — 12 mm lata. — 

 P. cymbifolius Fischer, 1. c. 



Fischer parts his P. cymbif. into two forms : f . subperfoliatus and f . subcrispus 

 yet without stating the separating differences. All materials from Ebing I have seen 

 are uniform and I propose to name the form after its meritorious discoverer Dr. 

 G. Fischer, Professor in Bamberg. 



Distribution. Germany, Bavaria, Mainaltung bei Ebing, 02, Fischer (hb. 

 Stockholm.). 



Real P. Gooperi is besides observed by us from Gudena in Denmark (hb. Baagoe). 



P. crispus L. X prjelongiis Wulf. 



Ex Caspary, Bericht etc. in Schriften Phys. Ok. Ges. Konigsberg 1878, 96—98. 

 — P. undidatus Wolfg. in J. A. & J. H. Sohultes, Mantissa in vol. tert. etc. 1827, 

 360, ex Raunki^r, Danske Blomsterpk I, 1896, 104. 



This hybrid can easily be distinguished both from the preceding bastard and 

 from the parent-species in the bicanaliculate stem and the even leaf-margin. At least 

 hitherto very few individuals of it have been discovered with rudimentary serrature. 

 The author has seen a single specimen from Langer See of West-Prussia. On such 

 individuals those dental rudiments, at all events, can be observed only in very young 

 leaves as they very soon disappear. On the contrary the leaf margin often appears 



