66 J. O. HAGSTROM, CRITICAL RESEARCHES ON THE POTAMOGETONS. 



Further, f. minor, with short internodes and small leaves; f. latifolius, broad-leaved; 

 f. angustifolius, narrow-leaved; f. cuspidatus with elongated, finely cuspidate leaves. 

 Probably he means a form called by J. Baagoe (in some herbaria) »f. cu.spidaia» 

 which on closer investigation has turned into the X P. bambergensis ; f. selenocarpus, 

 fruit inside with a basal boss as in P. acutifolius. It may be added that a micro- 

 carp form is also found. 



A form hitherto not studied is the above mentioned abortive form, f. albortivus m. 

 It has always abbreviated peduncles (15 — 25 mm), undeveloped spikes with only 5 — 7 

 verticils and barren flower parts. It behaves completely as a bastard and it is not 

 impossible that the properties just now mentioned may derive their origin from P. 

 acutifolius. If this were the case the reduced number of the middle vascular bund- 

 les of the peduncle also would be satisfactorily explained. In the vegetative parts, 

 however, no influence from P. acutifolius can be traced, but it is possible, that fu- 

 ture researches here also may discover what we at present are unable to discern. 



I have seen distinct examples of this interesting plant from Sweden, Uppla7id 

 in the following small lakes or water currents: Metsjon in Fasterna, 82, Tiselius 

 (hb. Stockholm, et Uppsal.), Sparren in the parish of Nartuna, 93, Tiselitjs (hb. 

 Stockholm, et Uppsal.), Valloxen 82, Tiselius (hb. Stockholm, et Uppsal.), Heder- 

 viken, 58, Tiselius (hb. Uppsal. et Lund.), Bergshamra in Kyrksjon, 78, Loegren 

 (hb, Lund.), Skeboan, 67, Mosbn (hb. Uppsal., Lund, et Gotenb.). — Stidermania, 

 for instance in Branningetrask near Sodertelje, and in Tumba kvarnsjo. On the oc- 

 currence of the supposed parent-species in those regions, see below ! 



But a similar plant is also collected in Scotland by Babington (hb. Stockholm, 

 et Uppsal.), where P. acutifolius is not now met with. Nevertheless it is possible 

 that it has occurred there in olden times. 



P. zosterifolius has an amphigean distribution. Sweden northwards to east 

 Jemtland, Barrsjon, 81, Tiselius (hb. Stockholm., Uppsal. et Lund.), f. major, and 

 south Angermania, Gudmundra at Frano, 70, Sjostedt (hb. Stockholm.) ca. 63° N. L. 

 To the south of this point it has an eastern distribution through Medelpad, Selanger 

 near Sundsvall, 24, L.sistadius and others (hb. Stockholm., Uppsal. and Lund.), f. 

 angustifolius, fruiting; Oestricia, Trosken at Gefle, 65, Theel and others (hb. Stock- 

 holm., Uppsal. et Lund.); Uppland, manj^ stations, for instance Norrsjon at Blad- 

 aker, 02, Ringselle (hb. Uppsal. et Lund.), Lomaren at Norrtelje, 80, Hedlund 

 (hb. Uppsal.), Satrasjon at Uppsala, 28, Wahlenbebg (hb. Uppsal.), Ekebysjon, 18, 

 Wahlenbekg (hb. Uppsal.), Fyrisan, 28, Wahlenbebg (hb. Uppsal.); Westmanland, 

 Kopingean, 48, »Lhte» (hb. Uppsal.); Sudermania, many stations, for instance at 

 Stockholm, collected by Nyman, Haktman, Thedenius and others (hb. Stockholm., 

 Uppsal. et Lund.), Nykoping, 51, Feistedt (hb. Stockholm.), Eskilstuna, 83, Pehes- 

 soN (hb. Lund.), Ardala, 50, Fbistebt (hb. Uppsal.) etc.; Nericia, Igeln in the pa- 

 rish of Skollersta, 70, Hartman (hb. Uppsal.), at Orebro, 69, Habtman and later 

 many others (hb. Uppsal. et Lund.); Ostrogothia, Norrkoping, 56, Hammaesten and 

 others (hb. Uppsal.), Himmelstalund, 67, Elmqvist (hb. Lund.), Soderkoping, 49, 

 »Lbg» (hb. Uppsal.), Linkoping, 24, Fries (hb. Uppsal.), Skrukeby and Svinstad, 



