248 J. O. HAGSTRÖM, CRITICAL RESEARCHES ON THE POTAMOGETONS. 



L. simillima (vide figuram 114!). Ligulce badise subecarinatae caducse, foliorum cau- 

 linorum 35 — 40 mm longae, ramorum breviores. Fruclus oblique semiorbiculatus ca- 

 rinatus stylatus, 3x2 mm. — Anatomia caulis, vide infra ! 



The anatomy oj the stem: Epidermis without bast-bundles and pseudo-hypo- 

 derma. Interlacunar bundles present in two circles or only one, the ligular circle. 

 Endodermis of ?<-cells as in P. luvens. Central cylinder presenting the oblong type. 

 Accordingly the stem-anatomy exhibits great resemblance or accordance to that of 

 P. dentatus, see the figure 115, Hl which, however, is endowed with a one-layered 

 pseudo-hypoderma. 



The leaf margin of P. distinctus is not described. It may be denticulate, but 

 it is probably smooth, since the serrulation of the Lucentes can be observed almost 

 by the naked eye. lf its leaf margin is destitute of denticles P. distinctus is to 

 be referred to another subsection. 



As to nervation the submersed leaves of P. bi form is are like those of P. di- 

 stinctus, thus described by Ar. Bennett »secondary nerves (not basal) produced along 

 the central ner ve about halfway up». This corresponds nearly with what is the 

 case of the stalked leaves of P. biformis, but the sessile leaves have a nervation 

 very much resembling that of a P. crispus-\ea,i. 



The plant here described is gathered in »Songaria-Siimpfe von Urdshar» and 

 East Asia may therefore be its distribution-area. 



P. malaianns Miqfel. 



Flore de 1'Archipel Indien 1870 — 71, 46. — P. mucronalus Presl, Epimelia? 

 Botanica- 1849, 245. — P. japonicus Franciiet et Savatier, Enumer. pl. Jap. II, 

 1879, 15 (nomen solum)? — P. Wrightii Morong, Bull. Torr. Bot. Club, 1886, 158, 

 t. 59. — P. Iretocarpus Maximow., ex Ar. Benn., Journ. of Bot., 1891, 154, et speo. 

 Petropol. — Fig. 115. 



This species approaches to P. lurens by its stalked, sharp-pointed, serrulate 

 submersed leaves, persisting ligules, and by the absence of floating leaves; but dif- 

 fers well from it by somewhat longer petioles (± 3 cm), narrower blades, and dif- 

 ferent nervation, the innermost nerve-pair forking from the midrib first at the 

 middlc, not at the base of the leaf. By this and by the stem-anatomy (central 

 cylinder), also, it shows affinity with P. uodosus and hindostanicus. By its styles 

 and stigmas again it approaches to /'. prrfoliatus, which species the fruit also 

 exhibits a great resemblance to. 



The stem-anatomy lacks subepidcrmal bast, but possesses 2 — 3 circles of in- 

 terlacunar bundles; epidermis-cells ehort, almost oubioal; the endodermis seems typi- 

 cally to be composed of faint //-cells, but has often longer or shorter stietehes 

 of ordinary o-cells (o- //-endodermis); central cylinder with all bundles free. The 

 prototype consequently is here more purely represented, by which the species can 

 be said to form fche one fcerminus of the group, while /'. gramineus forms the other. 



