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



This mode of branching dichotomously from the primary involucral leaves I ne- 

 ver saw in any other variety or form of the species. In general, only the inferior bud 

 of the two at the base of the peduncle becomes evoluted and furnished with a single 

 spike. In f. geminatus on the contrary the stem becomes forkedly branched by spici- 

 ferous branches of 1st to 3rd rank, considerably surpassing the primary peduncle, 

 which here is 60 — 70 mm long, thus a way of prolonging the stem which answers 

 to the type D, Fig. 2. For the rest the form is normal. 



Distribution of var. striatus: S. America, Chili, Lacus Pudaguel, 82, Philippi 

 (hb. Stockholm.). — Argentina, Jujuy, Laguna de Sansal, 01, Fries, n. 424 (lib. 

 Stockholm.), Casa Bamba, Sierra Chica de Cordoba, 09, Stuckert (hb. Haun.), P. dis- 

 similis Ar. Benn., authentic. — Bolivia, Gran Chaco, Caiza, 02, Fries, n. 1575 (hb. 

 Stockholm.), f. geminatus. — Ecuador, in Andibus, 1857 — 59, Spruce n. 5886 (hb. Stock- 

 holm.), f. geminatus. — Peru, Callao, 23 (hb. Christ. »dedit J. Syme»). 



P. pectiiiatiis L. x vagiiiatus Turcz. 



P. vaginatus X pectinatus ex Fontell, Von einig. Potam. Hybriden, 1902, 2. 

 — P. pectinatits X vaginatus ex Fontell, Beitr. Anatom. Bau Pot.-Art. 1909, 23. — 

 P. bottnicus Hagstr. 



Just as in the hybrid P. fennicus the grayish colour of tliis plant alludes to a 

 certain connexion with P. vaginatus, which fact, moreover, is ascertained by the 

 usually short, obtuse stem-leaves. Branch-leaves longer and narrower, but even these 

 commonly obtuse, though towards the apex more conspicuously tapering than in 

 P. vaginatus, someone or other acute or cuspidate as in P. pectinatus. Sheaths and 

 ligules intermediate. Ramification often as in P. pectinatits. The stem-anatomy 

 shows an influence from P. vaginatus by the presence of numerous vascular- and 

 bast-bundles in the bark. The central stele sometimes coincides with that of P. 

 pectinatus, sometimes almost with that of P. vaginatus. The evolution of the spikes 

 seems to draw near P. pectinatus, but is very much defective. 



This hybrid is first discovered by C. W. Fontell in the neighbourhood of Ja- 

 kobstad, Finland. From the Swedish coast of the Bothnian Gulf I know it from two 

 stations: the sound at Tyndero in Medelpad (near Sundsvall) and at Hernosand in 

 Angermania. Besides a plant from Suopohja, Russian Karelia (hb. Helsingfors, Finland) 

 might also be this hybrid (or P. fennicus). More stations are not hitherto known. 



The characteristics of all those are that the leaves for the most part are more 

 or less obtuse and more or less destitute of the light marginal border of P. vagina- 

 tus, that the ligule of the lower leaves are persistent and somewhat elongated, fur- 

 ther the numerous cortical strands of the stem and the more or less defective or 

 deformed fructifications. From X P. fennicus it differs in the coarser growth, more 

 abundant ramification, larger sheaths, broader leaves and more numerous bundles in 

 the bark of the stem. 



Distribution: Sweden, Angermania »ad oppidum Hernosand freto australi», 

 99 TiSELius (hb. Stockholm.), labelled P. vaginatus. — Finland (and Russia) see above! 



