KUNGL. SV. VET. AKADEMTENS HANDLINGAR. BAND 55- NIO 5. 



155 



70 to 80 mm long and 6 mm broad. In case the 

 specimens quoted under P. nodosus belong hereto, 

 these leaves are a little longer and broader than the 

 measures above stated. The base tapers petiole-like 

 or is short-petioled. Upper leaves longer stalked, 

 petioles of the floating leaves nearly equalling the 

 lamina. Submersed leaves quite Jacking a serrulation, 

 and only the midrib seems to be provided with lacunae. 

 — The materials, however, are rather scanty and 

 specimens with broader floating leaves may be found. 

 The stem-anatomy reminds much of P. nodosus 

 or alfinus by its 0-endodermis, free vascular bundles 

 of the central cylinder and the absence of interlacunar 

 bundles in the cortex. Someone or other strand 

 sometimes seems to occur subepidermally, though it 

 may not be the normal. Upon all accounts it seems 

 to be separate from P. nodosus as well as from P. 

 Nultallii; nor can it be, as I think, a cross between 

 these species, though the small, undeveloped spikes 

 might seem to indicate a hybrid origin of the plant. 



Distribution: America, Portorico, Aguas buenas, 85, Sintenis 

 (lib. Stockholm.); the label bears the following note: — »P. Sintenis: 

 Plantse Portoricenses no. 2537. P. pensylvanicus Willd. Aguas buenas 

 8. 9. 1885. Det. A. Bennett*. As it will be seen Mr. Bennett 

 has considered it to be P. pensylv. (= P. Nuttallii) and it is likely 

 to be the same or a similar form which Graebner (in Pflanzenreich, 

 1907, 56) has named P. Nutallii ■( portoricensis. Might this plant 

 of Puerto Rico be identic with the P. plantagineus var. jamaicencis 

 of Grisebach? 



A 



Fig. 72. P. imu- 

 laniis Hacste. A, 

 Floating leaf, \. B, 

 Top of submersed 

 leaf (enlarged). 



P. liiiirtostanicus n. sp. 



Caulis teres simplex, internodiis 6- 



Fig. 73. 



B 



Fig. 73. P. Iiiiid- 

 oslaniciisRAGsTU. ^, The 

 blade of a submersed 

 leaf showing the course 

 of the longitudinal nerves 

 (see the text!), '. B. 

 The top of a submei-sed 

 leaf showing the vena- 

 tion and the form of 

 the nervc-spaecs (some- 

 what enlarged). 



-8 cm longis, ramo prolon- 

 gatus. Folia submersa integerrima lanceolata longe et acute cuspi- 

 data longe petiolata ca. 15-nervia, laminis 100 — 120 mm longis 20 

 — 22 mm latis, petiolis ± 50 mm, superioribus ad 80 mm longis; 

 natantia lanceolata apice obtuse subcuspidata, 80x20 mm. Ligidm badiae subpersi- 

 stentes amplectentes, ad basin ± conspicue bicostatse, 40 — 50 mm longae. Pedunculus 

 sequalis ± 80 mm longus. 8pica florens 15 mm, deflorata 40 mm longa. 



As to shape the submersed leaves resemble the leaves of P. lucens. The 

 lateral nerves do not spring from the basal part of the midrib, but branch from it 



