130 



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



str 



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. S. Ajrica, »Zwarkopsrivier 1830» (hb. 

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



P. quinquenerviiis n. sp. — Fig. 57. 



Caulis ramosus elongatus, internodiis 2—5 cm (summo 

 4—8 cm), ramis spiciferis 1:« — 2:se ordinis prolongatus com- 

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

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

 dis utrinque duabus instructo, ramulina panlo breviora et 

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

 lata, petiolo laminis breviore, 7-nervia. Liguhv fissa? meni- 

 branaceoe cito evanescentes, ad basin glandulis oleiferis, in 

 spatio frontali 7-nervia3. Pedunculus 15 — 25 mm longus. 

 caule subcrassior. Spica 5-verticillata, densa. Appendiees 

 staminum rotundati, breviter unguiculati. Pistillum fere ut 

 in P. javanico. 



The habit, form and nervation of the f loating leaves 

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

 to which it is also rcckoned 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 /'. 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 (han in 

 /\ javanicus, probably also the fruit. Ovary verv conspicu- 

 ously keeled, style well developed and stigma oblong; its 

 point free from the style. (See the fig.!) 



Stem, like the pedancle, somewhat flattened, ils epi- 

 dermia furnished with a one-celled hypoderma, central oylin- 

 der's cross-cutform lanceolate-oval and the latera] bundles 

 distinotly separated fram the median onos. For the rest 

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

 midrib <>f the submersed leaves is on either side surronnded 

 by two rows of laeuna 1 and this lacunar pari is strengfhened 

 by foui- Bubepidermal bast-bundles in the usaal manner. 

 The specimens examined are oolleeted by Maideh in the Centennial Park, 



X. S. \V., Auslralia in IK97 (hl>. Stockholm.) and the speeies is Likely to be oonfined 



to this pari of the world. 



sti 



I .7 /' quinqiu ni ruins II IG 

 -i it. .1, Pai i «f a stem-leaf below 

 Di" middle -h<.>* ing i be i ttension 

 of the lacunar By a te na /) o\ i r the 

 leaf and the nervation, ','. B, Trons- 

 Bi .-Ii .1 this II al.-. ", I '. 



'i "|i "i a brancfa leaf, j\ /'. Pistil, 

 iew, tiic keel of Un- c\ ary 

 hatched, ',''■ '■• Tranw erse section "i 

 I be i' ti I), ',". /■', Trana- 

 Bi '-t min ni pednncle, Bhowing 

 ii.' -ii.- ut the vascolar bnndles, (t>£ 

 Ti an \ . i se si ction of a yonng 

 .i thi base, fe, frontfli let, : ', . 

 // ^ miiiii; ligali 



