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



197 



Distribution. N. America, »Brandscomb Pond St Johns* ^Morison Newf:d» 

 (hb. Stockholm.); "In paliidibus ad South Natick, Mass., U. S. A.,» 81, Morong (hb. 

 Stockhohn.). — The specimens from Pine plains, N. Y., leg. Hoysradt (hb. Stock- 

 holm.) must be considered the hybrid cjramineus X natans. 



P. Moroiigii Ar. Bennett. 



Notes on Potamogeton, in The Journal of Botany, 1902, 145. — Fig. 98. 



The specimens of the collections here preserved are deprived of fruit, but their 

 other organs answer rather exactly to the description, and their habitat is not far 

 from the localities recorded by Ar. 



us 

 m 



StT 





c25 



str 



'Ol 



B 



■ep 





Bennett, because of which I regard 

 my determination as correct. 



Floating leaves of our specimens 

 long-petioled (above 100 mm) with lan- 

 ceolate or oval laminse, 50—60 X 13—20 

 mm, the apex of which is a little 

 elongated, obtusely cuspidate. Ligules 

 45 — 55 mm long, persistent, with nu- 

 merous strong nerves, dark-brown or 

 greenish-brown, without ridges. Sub- 

 mersed leaves very narrow, faintly ca- 

 naliculate and 3-nerved, striate bj' the 

 numerous strong subepidermal strands. 

 The arrangement of those strands and 

 of the lacunar system is shown by the 

 figure added. 



Stem-anatomy much like the dia- 

 gram of P. natans: endodermis of more 

 or less one-sidedly thickened cells, two (three) circles of interlacimar bundles in the 

 bark and a full-numbered circle of subepidermal strands; epidermis witli a one-celled 

 strengthening layer. The bundles of the central stele arranged according to the 

 trio-type diagram. 



Distribution. Japan, Tokio, Prof. R. Yatabe (hb. Uppsal.). 



Subsectio 23. Lucentes Graebner. 



Caulis ut in pra3cedente. Folia infinia linearia ut in prseced., summa sa?po 

 coriacea, cetera semper membranacea lanceolata cuspidata, petiolata v. sessilia, serru- 

 lata; ligulse persistentes saepe fortiter bicostatse. Pistillum stylo brevi. Frnclus 



Fig. 98. P. Uorongii Ar. Benn. A, Blade of a floating leaf }. 

 D, Transverse section of a submersed leaf its, Is, m, n\ sir as in 

 tig. 97, ^i". C, Part of a transverse section of the stem, see the text, 

 *\ > ^P, epidermis, cc, central stele. 



