KUNGL. SV. VET. AKADEMIENS HANDUNGAR. BAND 55. N:0 5- 



157 



21-nervia, 90 X 30 mm, sub spica prim. 100 X 25, 19-nerv. Ligulce 40 — 50 mm longse, 

 bicarinatae, badise, membranaceae, in spatio intercarinali 15-nervise. Pedunculus prima- 

 rius ca. 90 mm 1., crassiusculus. Spica deflorata ca. 40 mm. longa. Folia perianthii 

 longe unguiculata. Pistillum breviter stylatum, stigmate oblongo. Fruetus 3,2 X 2,5, ± 

 carinatus, rostro brevi apicali v. subapicali, operculo rotundato. 



Anatomy of the stem: epidermis-cells about ten times as long as broad, two- 

 layered pseudo-hypoderma, no subepidermal or ligular bundles, O-endodermis, central 

 cylinder prototypic (see p. 162). 



The specimens examined are labelled: Uruguay, Paso Zapeyii, 01, Berro 

 (hb. Haun.). 



P. meinbraimceus n. sp. — Fig. 75. 



Caulis teres simplex ut videtur, ramo primse 

 ordinis prolongatus, internodiis elongatis, sub spica 

 primaria ca. 12 cm. longis. Folia omnia membra- 

 nacea, lanceolata, apice brevissime et obtuse mucro- 

 nulata, basi lanceolata vel ovali-lanceolata, 55 — 65 

 X 13 — 45 mm, integerrima, 13 — 15-nervia, nervö 

 medio reticulata, petiolata, petiolo 8 — 20 mm longo 

 angusto. Ligulce membranacese caduese fere ecos- 

 tatse, 25 — 30 mm longse in superiore parte caulis. 

 Pedunculus aequalis, ± 10 cm longus. Spica florens 

 15 mm longa densa. Pollen globosum parvum. 

 Pistillum breviter stylatum, stigmate parvo ovali 

 instruetum. 



The species described above is by Mr. Ar. 

 Bennett in Dr. Tiselii herbarium (now in hb. 

 Stockh.) united with his P. Cheesemanii. The latter 

 species, however, being characterized by a rich 

 produetion of floating leaves, can scarcely be 

 united with P. membranaceus, in which no trace 

 at all of such leaves can be observed. Besides, the 

 leaves are short-petioled and provided with an 

 obtuse little cusp, certainly very short but distinct. 

 Further they are broader and with more nerves 

 than the submersed leaves of P. Cheesemanii 

 swollen. Fruit not seen. 



The central C3dinder of the stem has eight to ten free vascular bundles and 

 0-endodermis. In the bark there is a cirele of bast- and vascular bundles, but no 

 subepidermal strands are observed. Epidermis without strengthening layer. 



The branch which prolongs the stem has unusually stretched internodes, the 

 lowest as far as 19 cm. The specimens examined are gathered in running water, 



ep 



[ Fig. 75. P. /nembranact us Hagstr. A Involu- 

 eral kat" with the crossveins left ont, j. B, The 

 top of the same, niagnified. C, Diagrammatic cross- 

 seetion of the stem, showing only the form of the 

 central cylinder and the arrangement of its bundles 

 and of the hundles of the bark, \ 5 , cc, central 

 cylinder, slr, cortical bundles, ep, epidermis. 1), 

 Pistil, side-view and from above, \ ? . 



Styles shorter and not so much 



