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



247 



Central cylinder intermediate, endodermis always of w-cells like the parents. It is 

 not known to me, if the Babington Irish plant of Lough Corrib, figured in Engl. 

 Bot. Suppl. t. 2847, entirely coincides with the Danish form. It seems not to have 

 been refound since the year 1835. Babington named it P. longifolius, and thus it 

 seems correct to keep the name for the Irish plant and write: 



f. longifolius (Bab.): »leaf-tip terminating in a point like those of lucens^ ; and 

 name the Danish plant : 



f. danicus n. f.: — Folia sessilia lanceolata basi attenuata 

 apice breviter obtuseque cuspidata margine Isevia. Pedunculus 

 subelongatus. 



Distribution: Denmark, Gudenaprope Randers, 96 Baagoe 

 and others (hb. Uppsal., Lund.); other forms from Gudena, f. 

 inst. at Kongensbro, are not this hybrid, but X P. decipiens, X 

 P. sterilis, X P. subrufus and X P. undidatus. Nibsa, 00, Baagoe 

 (hb. Stockholm.); Odensea, Fionse, 97, Baagoe, (hb. Stock- 

 holm.) ; also growing in Sneuma, Skalsa and Varming Lake (hb. 

 Hagstrom). 



On P. lucens X prmlongus |3 berolinensis AscH. & Graebn., 

 see above, p. 215! — 



In 1899, on investigating part of the Potamogeton collec- 

 tions of the museums of Bremen and Petersburg, I observed a 

 plant gathered by Alex. Schrenck in Songaria in 1840. I 

 had not an opportunity of describing it immediately and some 

 years later (1904) Ar. Bennett published his P. distinctus of 

 East Asia, which seems to have a close connection with, the 

 Songaria plant of Schbenck. Not having access to the type 

 of P. distinctus Ar. Bennett, I have not as yet succeeded in 

 clearing up the affinity or identity of the two plants. To judge 

 from the description of the fruit they are well distinguished hj 

 from one another, P. distinctus having the middle keel undulat- 

 ed and the lateral ones » produced here and there into small 

 knobs » etc. (Ar. Bbnn.) which is extraneous to the Songaria 

 plant. Leaving to the future to get the connection with P. di- 

 stinctus cleared up, I will here publish my remarks on the 

 interesting plant concerned: 



Fig. 114. P. bifoi-mis 

 iGSTB, A, Third leaf of n 

 l)r.anch (top and basal half) 

 showing the form and ner- 

 vation, J. B, 4th leaf from 

 the same branch (basal part). 

 ■|. C, 9th leaf of the same 

 branch, f. 7>, Leaf-margin, 

 Y. E. Fruit, f. 



P. biformis n. sp. (vel forma P. dislincti Ar. Benn.?). — Fig. 114. 



Gaulis ramosus teres habitu P. graminei L. Folia superiora coriacea ad for- 

 mam et magnitudinem lis P. graminei L. simillima; submersa angusta denticulata 

 breviter cuspidata, caulina ad basin in petiolum angustata, ramea parva, 20—40 mm 

 X 2 — 4 mm, biformia, inferiora petiolata, superiora sessilia basi rotundata iis P. crispi 



