KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 55. N:0 5. 



157 



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

 bicarinatse, badise, membranaceae, in spatio intercarinali 15-nervia3. Pedunculus prima- 

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

 longe unguiculata. Pistillum breviter stylatum, stigmate oblongo. Fructus 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, 0-endodermis, central 

 cylinder prototypic (see p. 162). 



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

 (hb. Haun.). 



P. meiiibraiiaceus n. sp. — Fig. 75. 



Caulis teres simplex ut videtur, ramo primes 

 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 — 15 mm, integerrima, 13 — 15-nervia, nervo 

 medio reticulata, petiolata, petiolo 8 — 20 mm longo 

 angusto. Ligulce membranacese cadiicse fere ecos- 

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

 Pedunculus sequalis, ± 10 cm longus. Spica florens 

 15 mm longa densa. Pollen globosum parvum. 

 Pistillum breviter stylatum, stigmate parvo ovali 

 instruct am. 



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 

 production 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 cylinder of the 

 0-endodermis. In the bark there 

 subepidermal strands are observed. 



The branch 



ep 



Fig. 75- P. lucmbi-anaceus Hagstr. A Involu- 

 crai leaf with the erossveins left out, J. B, The 

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

 section of the stem, showing only the form of the 

 central cylinder and the arrangement of its bandies 

 and of the bundles of the bark, Y', cc, central 

 cylinder, sir, cortical bundles, ej), epidermis. 7>, 

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



Styles shorter and not so much 



stem has eight to ten free vascular bundles and 

 is a circle of bast- and vascular bundles, but no 

 Epidermis without strengthening layer, 

 which prolongs the stem has unusually stretched internodes, the 

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



