100 



J. O. HAGSTRÖM, CR1TICAL RESEARCHES ON THE POTAMOGETONS. 



mm longis. Folia omnia petiolata laminis coriaceis ± tenuia; inferiora petiolis 

 longioribus laminis parvis, superiora petiolis brevioribus, ca. 75 mm longis, laminis 

 majoribus, 65 — 70 x 25 — 30 mm, ± 19-nerviis, oblongis, basi et apice rotundatis vel 

 apice subcuspidatis; petioli ± biconvexi. Ligulce 30—50 mm longa? subcaduca? basi 

 obsolete bicarinata?. Spica? desunt. 



Anatomy of the stem : Epidermis-cells of nsual form abont 3 — 5 times as long 

 as tlie width; one-celled pseudo-hypoderma; no subepidermal strands. Cortex of 



usual strncture with one circle of vascular and 

 bast bundles (abont twelve in nnmber). Endoder- 

 mis of O-cells. The central cylinder presents an 

 v b eight-bnndled diagram type. Bast-cells and other 



mechanical cells are few in number. 



Distribution. South Africa. Rhodesia, in 

 the Chimona River near the Lake Bangweolo in 

 stagnant water, Rob. E. Fries, 1911, n:o 091. 

 This is the only station from which this plant is 

 hitherto known. 



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Pig. 78. P. etagnorttm Haobtb. .1, Träns- 

 \.i-. sectioo of the stem, 6 ,°, cc, central eylindor, 

 /, lacnnar system, ri,, cortical bandiet), ep, epi- 

 dermis, A//, psendo-hypoderma. />', Transverse 



• ■ii or ii petiole sbowing the ftve principal 

 vascnlar bundles (pb), 1 1 • * - arrangoment of the 

 lacanar Bystem (/), tlie cortical bandles (>•//) and 

 iIm anbepidermal Btrauds (str), *,'• 



P. fibrosus n. sp. — Fig. 79. 



Catdis teres, 2 — 2,5 mm crassus. Folia supe- 

 riora oblonga vel ovato-lanceolata, brevissime et 

 obtuse cuspidata, 75 — 85 X 25 — 30 mm, 15—19- 

 nervia, nervö medio prominente, petiolata brunnca. 

 Ligulce inferne conspicue bicarinata3, ca. 40 mm 

 longa?. Spica deflorata 45 mm longa, verticillis 

 quindecim. Fedunculus ut in /'. natante. Fruetus 

 non visus. Anatomia caulis: vide infra! 

 Only the three top most internodes of a spike-bearing shoot have been accessible, 

 in habit very much resembling a top of F. natans, or any other species with similar 

 floating leaves. It seems as if the leaf-base would hardly assume the subcordatc 

 form characteristic to some other species. The styles and stigmas are overripr and 

 cannot, therefore, be described. Nevertheless the species can easily be distinguished 

 from all the other similar forms by the anatomic diagram of the stem. The epi- 

 demi is is provided with a one-celled strengtliening layer and numerous bast bundles. 

 [nterlacunarly there is one, and oommonly a faint beginning to a second circle of 

 vascular- and bast bundles. Endodermis of O-cells, central cylinder with S Eree vas- 

 cular bundles, each wilh strong bast elements along the endodeiinis and in tlie pith. 

 Tlios(^ strong open bundle-sheaths are exceedingly significant of this species. 



Tlie liabitnt of tliis plant is not surcly known to me. Tlie label bears only 

 a number, »91», but I am probably not mistaken, when supposing it to originate 

 from Soutb Africa. 



The specimen here concerned is kept in hb. Stockholm. 



