130 



J. O. HAGSTROM, CRITICAL RESEARCHES ON THE POTAMOQETONS. 



The plant differs from P. javanicus by the short internodes, the ligules and 

 the submersed leaves lacking the broad lacunar part on either side of the midrib. 



Distribution. 8. Africa, »Zwarkopsrivier 1830 » (hb. 

 Stockholm.). It is probable that the collector is Zeyher. 



P. qiiiiiqiieiiervius n. sp. — Fig. 57. 



Caulis ramosus elongatus, internodiis 2 — 5 cm (summo 

 4—8 cm), ramis spiciferis l:ee — 2:se ordinis prolongatus com- 

 pressus (2 : 1). Folia submersa linearia acuta, caulina 70 — 

 90 mm longa 2 mm lata, 5-nervia, nervo medio striis albi- 

 dis utrinque duabus instructo, ramulina paulo breviora et 

 angustiora 3 — 5-nervia, natantia lanceolata ± V mm, petio- 

 lata, petiolo laminis breviore, 7-nervia. Ligulm fissse mem- 

 branacese cito evanescentes, ad basin glandulis oleiferis, in 

 spatio frontali 7-nervi8e. Pedunculus 15 — 25 mm longus, 

 caule subcrassior. Spica 5-verticillata, densa. Appendices 

 staminum rotundati, breviter unguiculati. Pistillum fere ut 

 in P. javanico. 



The habit, form and nervation of the floating leaves 

 etc. of this plant coincide nearly with those of P. javanicus 

 to which it is also reckoned by Ar. Bennett (as a var. 

 major) in Graebner, Potamog. 1907, 161. On closer exa- 

 mination, however, it is clear that the plant considerably 

 differs from the Kunene-form, considered also by the same 

 eminent author to be the var. major of P. javanicus. It is 

 not only in all parts larger, but the submersed leaves have 

 also another lacunar system and apexes of a different shape 

 as the figure evidently shows. The pistil is stouter than in 

 P. javanicus, probably also the fruit. Ovary very conspicu- 

 ously keeled, style well developed and stigma oblong; its 



Fig. 57. P. nnlnquencruins H.\G- • j_ j? i» ji j ^ /c* jl r* i\ 



. A, Part of a stem-leaf below pomt free from the Style, (bee the fig.!) 



the middle showing the extension 

 of the lacunar system il) over the 

 leaf and the nervation, y, B, Trans- 

 verse section of this leafe, ^. C, 

 Top of a branch leaf, {'. 23, Pistil, 

 side-view, the keel of the ovary 

 hatched, ^-^. E, Transverse section of 



stem (see the text!). 



F, Trans- 



Stem, like the peduncle, somewhat flattened, its epi- 

 dermis furnished with a one-celled hypoderma, central cylin- 

 der's cross-cutform lanceolate-oval and the lateral bundles 

 distinctly separated from the median ones. For the rest 

 the stem exhibits the usual structure (see the fig.!). The 

 midrib of the submersed leaves is on either side surrounded 

 by two rows of lacunae and this lacunar part is strengthened 

 by four subepidermal bast-bundles in the usual manner. 

 The specimens examined are collected by Maiden in the Centennial Park', 



N. S. W., Australia in 1897 (hb. Stockholm.) and the species is likely to be confined 



to this part of the world. 



verse section of peduncle, showing 

 the site of the vascular bundles, (rh) 

 ^j, G, Transverse section of a young 

 ligule at the base, ic, frontfield, \^. 

 //, Young ligule, y. 



