KUNGL. SV. VET. AKADEMIENS HANDLINGAK. BAND 55. N:0 5. 195 



above, a characteristic modification of the nato?i5-Ieaf and trichoides-leat, similar to 

 both by its abundant scleronchyma. 



Finally it may be stated that P. trichoides predominates in the structure of 

 the ligules, often in the tops of leaves too, whereas P. natans is prevailing over P. 

 trichoides for instance in the number of pistils, here being four, not as in the latter 

 a single one. The shape of ovaries seems to approach to P. trichoides. As to the 

 ramification it is met with now trichoides-\i\ie, now natons-like. 



It is interesting to observe as how, at crossing, a M-endodermis most often pre- 

 vails over an O-endodermis. If therefore, as some authors assume, P. lanceolatus 

 Sm. (see p. 149!) were a crossbreed of P. gramineus with mucronatus or pusillus, we 

 should expect to find a M-endodermis, especially as P. gramineus has very prominent 

 tt-cells. Instead of it we here find an O-endodermis. 



Distribution. France: »Gironde, In fluvio Leyre prope Mios. Julio 1899 leg. 



E. J. Neyraitts (hb. Lund.); sin rivo prope Uza, Dpt Les Landes Endress 



Junio 1831 » (hb. Uppsal.). It is noticeable that this hj'brid has been able to stay 

 in those regions from its first discovery up to our days, a period of more than a 

 century. 



P. Ricliardii Solms Laubach in Schweini<'urth, Beitr. Fl. Aethiop. 1867, 194, 292. 



It seems to me that this species by its morphological and anatomical characters 

 comes very near to P. natans, to which it has also been referred by Schimpee. It 

 reminds also of P. nodosus and some species of the amflifolius-gvow^ (P. fibrosus). 



The two specimens here preserved were collected in a deflorate state without fruit. 

 — Stem stout and thick, a little branched, and prolonged from the axils of the in- 

 volucral leaves by an undeveloped branch; internodes shorter or longer (40—140 mm), 

 shortest below the primary spike. Inferior (or lowest) leaves linear, almost filiform, 

 the following petioled with more or less coriaceous, oval — ovate-oval, or sometimes 

 a little cordate-ovate (fol. flor.), red-brown or leather-coloured lamina of the size of 

 70 — 100 X 40 mm, about 20 — 25-nerved with obtuse mucro. Petioles long, broad, 

 those of the lower leaves a little longer, the topmost somewhat shorter than their 

 blades. Ligules 40 — 50 mm long, brown, with ridges only at the base, soon decaying. 

 Peduncle even, 70 mm long; spike 40 mm. 



Stem-anatomy : Epidermis with a one-layered pseudo-hypoderma but no (or a 

 few), subepidermal strands, in contradistinction to P. natans being provided with a 

 full-numbered circle of subepidermal bast bundles. Three circles of bundles in the 

 bark. 0-?f-endodermis. The bundles of the central axis arranged according to the 

 trio-type. 



This anatomical diagram distinguishes it both from P. natans and from P. 

 nodosus and P. fibrosus. From the former it is besides separated by the broader 

 petioles, the abundance of floating leaves below the primary spike, by browner and 

 soon decaying ligules, narrower submersed leaves, and stouter stem. The ripe fruit 



