94 J. O. HAOSTRÖM, CRJTICAL RESEARCHES OX THE POTAMOGETONS. 



Uppsal., Lund., Gothenb.), Närtuna in Trehörningen, 95, Wedberg & Tiselius (hb. 

 Stockholm., Uppsal., Lund.). — Jemiland, Hammerdal, Viken, 83, Jönsson (hb. Lund.), 

 northern-most station, year-is. + 2° C, Hassjö, Juleby (hb. Stockholm.). 



Denmark, Bornholm, 68, Nielsen and others (hb. Stockholm., Uppsal., Lund., 

 Gothenb.). — Finland, Karelia oneg., 63, Simming (hb. Uppsal.). — Germany, Usedom, 

 54, Marsson; Kiel, Nolte (hb. Stockholm., Uppsal.). Bavaria, prope Altneuhaus, 05, 

 Fisciier (hb. Stockholm), prope Adelsdorf, 05, Fischer (hb. Stockholm.), 49° N. L. — 

 Russia, In lacubus prope Vilnam, hb. Besser (hb. Stockholm.). — Asia Pamir: Jashilkul. 

 98, Paulsen (hb. Haun.). — N. America, Nipigon, Lake Superior, 84, Macoun (hb. 

 Stockholm.). 



P. rutilns Wolfg. x Vaseyi Robb. (P. gemmiparus (Robb.) Morong in Bot. 



Gazette, 1880, 51). 



Some specimens from »Fastern Mass., U. S. A., Coll. Th. Morong >, now in 

 Uppsala museum, undoubtedly are the above written hybrid. Hitherto they have 

 been considered to be a distinct species and are as such figured in Morong, Naja- 

 dacese, 1893, t. LIV. They present so great resemblances to P. Vaseyi to the form 

 and structure of the leaves as well as to the turios that they necessarily must stånd 

 in close affinity to this species (fig. 59). Other properties as for instance the size and 

 the longer outer leaves of the turios, the length of the peduncle, the ligules, stem- 

 sclerenchyma etc. denote P. rulilus. The sterility and sporadic occurrence indicate 

 also a hybrid origin and I am waiting no serious objection to my supposition of 

 P. rutilns X Vaseyi. 



P. mncronatas Schradbe, ap. 



Reichenbach, Iconcs fl. Germ. et Helv. VII, 1845, 15. — /\ pusillus var. 

 interruptus Schultes, Oesterr. Fl. 1814, 328. — P. compressus p tennis Wahlenb., 

 Fl. upsal. 1820, 60. - P. compressus P élongatus Wahlenb., Fl. suec. 1824, 107. — 

 l\ compressus p acutus Sohlbcht., Fl. berolin. 1823, 117. — l\ pusillus v. A. Ciiam. 

 et Sohl., Linna3a II, 1827, 171. — P. pusiUus a. major Fries, Nov. Fl. suec. 1828, 

 48. — P. Friesii Ruprecht in Beiträge zur Pflanzenkunde d. russ. Reiches 1845, 43. 

 — P. Oederi Mkykr, Fl. hannov. excurs. 1849, 536. - P. major Morong, Najadacca 1 

 1893, 41. - Fig. 37. 



In habit this .species is very much like P. panormitanuå by the scarce occur- 

 rence of branches for the prolongation of stem according to the water-level. Usually 

 there is a spike-bearing branch in the axil of the uj)per involuoral leaf and this 

 braneh oltcii strelehes its internodes. This branch rarely bears a branehlet, and bran- 

 clics of the third rank niight not af all grow ont. The plant rather stretches the 

 to|)rnos) internode thuB Eollowing an eventual rising of the water. From the leaf- 



