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



sive than in P. zoster if olius. Stem-leaves usually more like P. acutifolius as to their 

 lacunar part. This form could be named 



f. iiiollifolius n. f. — Pars foliorum lacunosa ut in P. acutifolio. — 



Other individuals, as to the leaves more approaching P. zosterifolius with more 

 prominent midrib and less expanded lacunar system could be called 



f. strictior n. f. — Pars lacunosa folii magis ut in P. zosterifolio, folia ergo 

 strictiora. 



Stem usually thinner than in P. zosterifolius but in this case, again, as to the 

 margins more zosterifolius-\\ke. 



On the supposed bastard origin of the P. zoslerif. f . abortivus, see p. 66 ! 



Distribution: Sweden, Uppland, at Stockholm, Brunnsviken, 55 Cleve (hb. Stock- 

 holm.), poor material; same station, 90, Hesselman (hb. Stockholm.), Drottning- 

 holm, 07 Lagerm^all (hb. Stockholm), Sigtuna, Snorin, 80, Floderus (hb. Uppsal.); 

 Ostrogothia, Svinstad, Ekeroth (hb. Uppsal.), Hb. Normale V, 79, labelled: P. acuti- 

 folius; but with zoster if oliusAWe nervation and intermediate spikes and peduncles 

 (f. strictior Hagstr.); Scania, Kristianstad, 57, Olsson (hb. Gothenb.), 76, Nilsson, 

 and 87 Thedenius (hb. Uppsal.). 



Denmark, Hjulby mose, Fyen, 97, Baagoe (hb. Stockholm.). Germany, »Saxon. 

 HiJB.NER» (hb. Stockholm.) » Silesia, Vratislavise, Margarethendamm », 64, Uechtritz (hb. 

 Stockholm.). Another plant from »Bischofwald, 80, Uechtritz» (hb. Lund.) is more 

 doubtful. True P. acutifolius from Bischofwald is preserved in hb. Stockholm. 



Subsectio 8. Monogyni Hagstr. 



Caulis teres filiformis. Folia angustissirae linearia acutissima trinervia, basi 

 apiceque attenuata. Ligulce semper fissse ut in prsecedente, convolutse, in spatio in- 

 termedio 3 — 5-nervi8e. Pistillum stylo brevissimo, stigmate ovali. Fructus ssepe 

 dorso rugosus. 



Only one species belongs to this group presenting close relationship to the 

 next foregoing. Especially the style, stigma, and ripe fruit are conspicuously a like. 

 The abundance of leaf-sclerenchyma is common to the three groups: Conipressi, 

 Monogyni and Ochreati. 



P. triclioides Cham, et Schlecht. 



De plantis in exped. specul. Romanzoff. observ., in Linneea 11:2, 1827, 175, 

 t. IV, fig. 6. — P. condylocarpus Tatjsch in Flora XIX, 1836, 423. — P. tuberculattis 

 Tenore et GussoNE, Syll. Flora Neapol. App. V, 1842, 4, in Act. Soc. Borbonica 

 di Napoli I, 430. — P. monogynus Gay, ap. CossoN et Germain, supp. cat. rais. 

 1843, 89. — P. danicus Gandoger, Pugillus plant, nov., Osterr. Bot. Ztschr., 1881, 18. 

 — P. perneglectus Gandoger, 1. c. — P. orthorrhyncus Gandoger, 1. c. — P. Bce- 

 nitzii Gandoger, 1. c. ? — P. Phialas Post, Bull. Herb. Boiss. I, 1893, 409. — Fig. 29. 



