252 J. O. HAGSTRÖM, CRITICAL RESEARCHES ON THE POTAMOGETOSS. 



foliis lineari-lanceolatis». The note of the label is evidently directed to Prof. E. 

 Fries, who on a separate label autographically has added: »Potamogeton salicifolius 

 Wolfg. ex Fr. S. V. Se! Angermannia LiESTADius. » Afterwards Hartm., Skand. 

 Fl., has recorded, after Fries, Kengis as the single station of P. salicifolius, which 

 according to both Hartman's and Fries' earlier (ef. Fr. Nov. 2. 41) views has 

 been looked upon as P. prcelongus. With this »P. salicifolius* Hartman låter on 

 united a »(3 lanceolotus* , comprising partly forms of P. gramincus, partly also of the 

 hybrid P. nitens (see above!). — Lapland, Lap. pit., 23, Ljest. (hb. Stockholm.), »P. 

 salicifolius Fr. S. V. Se.», »P. prcelongus ,3 graminifolius Hartm. »; Arjeploug, 24, 

 LiEST. (hb. Uppsal.), hb. Hartman, by Ljest. named »P. grantineus v. lanceolalus*, 

 to which Hartman has added the following parenthesis »(v. boreale L. V. Ac. H. 

 1825)», narrow-leaved (stem-leaves 15 mm broad) ; Lp tornense, Dr. Deutsch, hb. 

 Z:dt. (hb. Lund.), Karesuando, L^est. (hb. Stockholm., Uppsal.). 



According to Sciieutz, Pl. vase. Jeniseens., this species is gathered by H. \V. 

 Arnell in the Nikandrovskij island situated in the Gulf of Yenesei 70° 20' N. L., 

 which is its most northern habitat. From this northern limit it descends to the 

 south and is met with in the Faröe Islands, Shetland Islands, British Isles, Den- 

 mark etc. through Europé to the Jura Mountains, Switzerland (Lac de Failléres, 

 Godet, hb. Uppsal.) and the Alps, and through A sia, Japan (Moraran, Ezo, 42° 10' 

 N. L., Coll. Pére U. Faurie) to the year-isotherm of about + 12° C. (inner Asia 

 probably 10° or 5°) and in North America the southern boundary seems to be the 

 same (ef. Britton and Brown, 111. Fl. etc, 1896, I, 71 !). 



Subsectio 25. Perfoliati. (Graebner) Hagstr. - /'. perfoliatus-grouj} 



Raunkueb. 



Caulis ut in proccedente. Folia omnia submersa membranacea sessilia amplexi- 

 caulia vcl infima basi rotimdata, apice ± canaliculata serrulata; ligulse breves eco- 

 statae valde caducee vel in fibrillas cito scissa?. Pistillum ut in prsecedente. Fructus 

 magnitudine media, vivus dorso rotundatus. — Anatomia caulis: 0-endodermis, fasci- 

 culi libriformes vascularesque corticales typice desunt. Fasoiculi mediani tubi cen- 

 tralis ut in Fig. 1 C dispositi. Praefoliatio convoluta. Turiones rhi/omatici obvii. 



This group includes a few nearly allicd species united formerly into one spe- 

 cies, P. pcrfolialus, but lalcly, by P. A. RYDBERG and M. L. FERNALD detaohed 

 from the genuine P. perfolialus and established as separat c Bpecies. Of thosc /'. 

 Uichardsonii is a comparatively better marked form than P. buphuroides, which 

 perhaps rather might be put as a Bubspecies under /'. perfoliatus L. 



As to the Btem-anatomy they are all quite like, thus behaving almost as the 

 species of the group Polygonifolii, and you will have no help from t lie inner struo- 

 ture of the stem in distinguishing the species from eaoh other. They are all non- 

 sclerenchymatous plants in oontradistinotiou to the preceding group. [t is notioeable 

 t hat P. Richardst » n ii with its strong ligular fibers nevertheless is devoid of ligular 



