KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 55. N:0 5. 97 



a little in yellowish, somewhat longer and more persistent ligules, more elongated but 

 obtuse leaf-apexes, and often longer peduncles, by which all it reminds of P. mucro- 

 natus, while the rest, the stem-anatomy, too, belongs to the P. ohtusifolius. I have 

 also seen the same singular form from the Krageholm-Iake in Scania, where it grows 

 together with P. ohtusif. of usual habit and P. mucronatus. Cfr. E. Fkies, Nov. F1. 

 suec. 1828, 48! I hold this also to be P. semifrudus. The youngest ligules in their 

 basal part connate and reminding of those of P. mucronatus (interm.). The Friesian 

 variety-name lacustris should be kept for this form, which may be identic with P. oh- 

 tusifolius V. fluvialis Lange et Mortensen, Bot. Tidskr. 1878, 200. 



The first-mentioned form is collected by Dr. Hartman in 1821 in the Holma- 

 river in the parish of East Vingaker, Sudermania, and may be named f. olivaceus n. f. 



P. iiiucronatiis Schr. x p.iiiormitamis Biv. (P. confinis n. hybr.). 



Caulis ± compressus. Folia angustissima ± rigida acuta, 3-nervia. Ligulce inter 

 parentes medium habentes sed costulis subviridibus. Hybernacula cum iis P. panor- 

 mitani subcongruentia. 



The forms here considered present a somewhat compressed stem, narrow stiff 

 leaves with sharp points, persistent ligules, at least in young state with greenish 

 costal stripes. Hereby they remind of P. mucronatus, but the turios have the same 

 shape as in P. panormitamis. They evidently derive their origin from the above 

 written parent-species. Leaves small and 3-nerved locally with indications of an 

 external side-nerve. In habit they are a P. mucronatus in miniature. 



Distribution. Sweden, Uppland, near Uppsala, »Hvithulfsbergi>, lib. Wahlen- 

 BERG (hb. Uppsal.); Rivulet between Kvarnbo and Haga, 1818 (Wahlenberg?), hb. 

 Th. M. Fries (hb. Uppsal.) probably P. mucronatus x pusillus. Vaksala near the 

 church, 95, Hellsing (hb. Lund.), very likely the same station as the first written. 

 — A specimen from Ostrogothia, Linkoping, Kattbrunnen, 63, Blomberg (hb. Upp- 

 sal.) also seems to be the same hybrid. 



Denmark, Helsingor, Marienlyst (hb. Lund.). — Holland » Amsterdam, Kalfje in 

 Teichen bei Amsteb, 83, Tiselius (hb. Stockholm.). 



P. imicronatus Schr. x pusillus L. (P. piisilliformis Hagstr. nov. nom.). 



P. intermedins Fischer, Die bayer. Potamog. in Ber. bayer. Bot. Ges. 1907, 

 28, 122.^ 



Part of the material going under the name of P. Berchtoldi Fieber belongs to 

 this hybrid. See, under P. pusillus, below! It is not by far so difficult to identifj^ 

 as the just described. Stem somewhat compressed, almost fihform, the ramification 

 from the involucral leaves sometimes like the one, sometimes the other of the parent- 



^ As the name P. intennedius was earlier applied by Chamisso and Schlechtendal, Linnoea 1827, 221, to 

 a plant from Landstuhl, probably P. poIi/yonifoUus, a new name must be chosen for tliis hybrid. 



K. Sv. Vet, Akntl. Hnndl. Bund 65. N:o 5. 13 



