KDNGL. SV. VET. AKADEMIENS HANDLINGAE. BAND 55. N:0 5. 



23 



B 



Fritsch notes, that it is not identic with P. flabellatus according to Fryer's de- 

 scription. C. Raunki^r (Danske Blomsterpl. Naturhist. 1896, 73) is in doubt of 

 its specific rank and rather piits it near to P. filiformis v. alpinus Bl. In this 

 G. Fischer (Bayer. Potamog. 1907, 130) also agrees, making of the two (regarded 

 as subspecies) a collective species »P. marinus autt. » On the misconception of v. 

 alpinus Bl., see p. 17. 



Many years ago I have come to the opinion below expressed about these 

 plants and in order to get the question critically elucidated I had written to Prof. 

 P. Graebner before the publishing of his Potamogre/ow-monography. Meanwhile I 

 have been misunderstood. He has considered it to be about a plant, here below 

 referred to P. strictus, whereas I had the European plant P. juncifolius in view (P. 

 Graebner, in Pflanzenr. 1907, 124, 162). 

 The facts which, as it seems to 

 me, decidedly prove its hybrid origin 

 are 1) the sporadic occurrence. Beside 

 the first named locality it seems to 

 occur in but two more places : Kongeaa 

 and Skalsaa in Jutland. Moreover the 

 specimens from these three stations (Inns- 

 bruck, Kongeaa and Skalsaa) are not 

 quite identic, although they may be 

 brought without inconvenience under the 

 same denomination. 2) The abundantly 

 developed vegetative system with rhizo- ^..^ ^ ^ p ^„,,..„^. ^ ^-„.„„.,. g,^,,^ ^ Leaf-.,pex, com- 



mas and turios in fellowship with a ">"» ^'^''^P''. ¥• 5. Leaf-apex, pecthmtus-sbuped, V (material from 



. m • Giessen, leg. Sakntheim). C, Transverse section of a leaf, \°, a the 



very rare occurrence of fruits. This miarib surronnaed by small lacanas, b, marginal nerves, /, the large 

 t , • , ■ 1 1 t /-^ -r:i channel-row (marterials from Giessen). 



characteristic has also made G. Fischer 



think of a hybrid origin. Later, after finding freely fruiting individuals at Murnau 

 he has attributed the sterility to swiftly running water. But if this might some- 

 times be disadvantageous to the fertilization, we cannot from this fact explain 

 either that the few developed fruits after examination always seem to have 

 impotent embryo nor the sterility of the pollengrains. The fruiting plant of Murnau 

 I have seen (lib. Stockh., see above! p. 19) is P. /^7^7orm^sPERS. var. rmco^Ms Hagstr. 

 Finally 3) this plant is wanting original characters. All its characters belong either 

 to P. filiformis or to P. pectinatus. Of the latter we are reminded by the numerous 

 internodes and their length, the thickness of the stem and branches with abundant 

 evolution of vascular- and bast-bundles in the cortex, particularly in the Kongeaa- 

 plant, the width of the leaves and the length of the sheaths sometimes but rarely 

 also the leaf-apex, that I, after seeking assiduously, really once have found pro- 

 vided with a little wart or slight cuspis (specimens from Giessen coll. by Sarntheim, 

 lib. Lund.), the 4 — 6 verticils of the spikes with comparatively short intervals and, 

 further, with respect to the anatomy of the stem, the endormis composed of strong 

 one-sidedly thickened u-ceWs. We are, on the contrary, reminded of P. filiformis 



