I 



KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 55. N:0 5. 65 



connects it with the Ochreati, with which it besides has the round leaf-base in com- 

 mon. The front-field of the ligules 25— 30-fibrous reminding also of the Ochreati. 



The evolution of rhizomes of this and some following groups is very inconsi- 

 derable and often quite failing. 



P. zosterifoliiis Schtjm. 



Enumer. pi. Ssell. I, 1801, 50. — P. complanatus Willd., Magaz. Ges. der na- 

 turforsch. Freunde Berlin, V, 1809, 297. — P. laticaulis Wahlenberg, F1. suecica 

 I, 1824, 107. — P. cuspidatus Sghrad., ap. Smith Engl. Fl. I, 1824, 234, ex Cha- 

 Misso. — P. zosterophyllus Dumortier, FI. belg. 1827, 164. — P. compressus L. ap. 

 Fries, Nov. Fl. suec. 1828, 44 — 46. — P. carinatus Kupffer ap. Von zur Muhlen, 

 Die Potamogetonen des Ostbaltikums in Korr. Bl. Nat. Ver. Riga, 1906, 164. — 

 Figs. 25, 26. 



According to P. J. Beurling, Syn. 1853, 89, the Wahlenbergian name refers 

 to P. zosterif. For this the fact also pleads that the just mentioned species appears 

 in several examples in the herbarium of Prof. Wahlenberg (lib. Uppsal.) while P. 

 acutifolius is wanting. 



Although I have not seen and examined the original P. carinatus Kupffer, I 

 consider it, according to the description, to be the species of Schumacher. A new 

 species is not to be thought of. Nor can it be a bastard, since the pollen is well 

 developed (» pollen optime evolutum»). Nor can it be a variety of P. acutifolius 

 which is neither many-flowered nor has elongated peduncles as P. carinatus is said 

 to have. 



The anatomical structure of the stem and leaf is showed by the figs. 25 and 

 26. The peduncle (Fig. 25) has scattered subepidermal bast-bundles, in some indivi- 

 duals rather numerous, in others very few. The number also decreases towards the 

 spike, thus the basal cross section showing more strands than the upper one. The 

 median vascular bundles vary in number from 2 to 4, the latter number when fruit- 

 ing richly, the former in case of spare fruit. The abortive form (see below!) never 

 exhibits more than two median bundles, the phloem part of which seems to have 

 been transformed into mechanical tissue.* The bundles of the stem, again, are all 

 normal. The lateral bundles of the peduncle are alvpays two, one on either side of 

 the middle ones, more or less approaching to the borders of the peduncle. In the 

 abortive form the lateral bundles also exhibit an abnormal appearance. Herein I 

 see the natural cause of the reduced ability of stretching the peduncles, of the re- 

 duced number of flowers, and of the incapacity of full development of the floral parts 

 of this form. 



G. Fischer has distinguished following forms of this species: f. major, of high 

 growth and with long leaves (= f. major Zapalowicz, Consp., 1906). To this belongs 

 a barren form which Tiselius (Pot. suec. exs. II, 1895, n. 97) has named f. magnus. 



^ For want of fresh material (he researches of this strange fact are not finished. 



K. Sv. Vet. Al<ncJ. Ilamll. Baiul 65. N:o 5. 



