80 J. O. HAQSTROM, CRITICAL RESEARCHES ON THE POTAMOGETONS. 



shorter peduncles (20—35 (60) mm) with only two (somethnes barely one) lateral vas- 

 cular bundles (fig. 30, F), without subepidermal bast-bundles, longer and more curved 

 styles and on the sides also rough or knobby fruits. They seem to stand in a si- 

 milar relation to each other as for instance P. zosterifolius and acutifolius, or the 

 south-american P. polygonus and Ulei. This form can in short be described thus: 



P. fnrcatllS n. species (vel subsp. P. ochreati?) 



Caulis superne dichotome ramosus ssepe ramis 4'®— 5* ordinis. Folia perspicue 

 cuspidata, fusco-viridia. Stylus elongatus subcurvatus. Fnicius rotundatus, carinatus, 

 lateribus et ventro rugosus, rostro apicale. — Anatomia, vide supra ! ^ Fig. 30, F — K. 



Distribution: Australia felix N. H. (hb. Stockholm.); unknown locality (hb. 

 Lund.). Tia river near Walcha, N. S. W., 97, Maiden (hb. Bot. Gardens, Sydney). 



Subsectio 10. Polygon! Hagstr. 



Caulis compressus vel teres, internodiis brevissimis, nodis sine annulo. Folia 

 linearia multinervia, media in parte late loculosa, basi ± rotundata, in apicem acutum 

 vel subobtusum sensim attenuata. Ligulce apice rotundatse semper fissse. Pislillum 

 stylo conspicuo incrassato, stigmate parvo. Fructus siccus tricarinatus, lateribus levis. 



Hereto belonging species can scarcely be arranged together with any of the 

 foregoing or following groups. The characteristic short internodes, the leaf- and 

 stem-structure, and especially the incrassate styles undoubtedly make them form a 

 separate group. The endodermis consists of 0-cells as in all similar species. 



P. polygonus Cham, et Schlecht. 



De plantis in exped. specul. Romanzoff. obs. — in Linnsea II: 2, 1827, 184. Tab. 

 IV, fig. 11. — Fig. 31. 



The species is easy to recognize on the very short internodes, by which it has 

 a certain exterior resemblance to P. Rohhinsii. 



The stem of this species, like that of the foregoing, is a little flattened and 

 prolongs itself often by branches of different (1— 4th) ranks from the uppermost leaf- 

 axils. The epidermis-cells of the stem are rather long, about 4 — 6 times the width 

 and supported by a one-celled stratum of bark-cells. Beside the usual subepidermal 

 strands there is also a number of thin interlacunar strands laterally placed, by which 

 this species (and the next following) differs from all the other narrow-leaved species 

 hitherto known. The bundles of the central axis are very conspicuously separated 

 in three groups, usually with two free bundles in either of the lateral groups, but 

 sometimes fused into a compound bundle. Stele-diagram: a reduced trio-type. — In 

 the peduncle the diagram shows numerous vase, bundles and subepid. strands. 



