74 J. O. HAGSTRÖM, CR1TICAL RESEARCHES ON THE POTAMOOETONS. 



si ve than in P. zosterifolius. Stem-leaves usually niore like P. acutifolius as to their 

 lacunar part. This form could be named 



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



Other individaals, 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 /\ zoslcrifolio, 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. i. abortivus, see p. 66! 



Distribution: Siveden, Uppland, at Stockholm, Brunnsviken, 55 CLEVB (hb. Stock- 

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

 holm, 07 Lagerwall (hb. Stockholm), Sigtuna, Snörin, 80, Floderus (hb. Uppsal.); 

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

 folius; but with zosterifoliusAike nervation and intermediate spikes and peduncles 

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

 and 87 Thedenius (hb. Uppsal.). 



Den/mark, Hjulby mose, Fyen, 97, Baagöe (hb. Stockholm.). Gcrmany, »Saxon. 

 Hubxer» (hb. Stockholm.) >Silesia, Vratislavia), 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 fiiiformis. Folia angustissime linearia acutissima trinervia, basi 

 apiceque attenuata. Ligulce semper fissae ut in pra?cedente, convolutae, in spatio in- 

 termedio 3— 5-nerviöe. Pistillum stylo brevissimo, stigmate ovali. Fruetus sa?pe 

 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 fchree groups: Compressi, 

 Monogyni and Ochreati. 



I\ trichoides Cham. et Schlboht. 



De plant is in exped. specul. Romanzoff. observ., in Linnsea [1:2, 1S27, 175, 

 t. IV, fig. 6. P. eondylocarpu8 Tausch in Flora XIX, 1836, 423. P. tubcrculatts 

 Tenore et Gussone, Sy 11. Flora Neapol. App. V, 1842, 4, in Act. Soc. Borbonica 

 di Xapoli I, VM). /'. monogynus Gav, ap. Cosson et (Jebmain, aupp. ca(. rais. 



1.843,89. /'. danicus Gandogeb, Pugillus plant, nov., öeterr. Bot. Ztschr., L881, 18. 

 — /'. perneglectus Gandogbr, 1. c. - P. orthorrhyncus Gandogir, 1. c. — /'. JUv- 

 nitzii Gandoger, I. c! P. PAioZos Post, [»ull. Herb. Boiss. [, 1893,409.- Fig. 29. 



