38 



J. O. HAGSTROM, CRITICAL RESEARCHES ON THE POTAMOGETONS. 



end 



str 



sed validse, persistentes semper fissse badeo-virides, ut ligulae marginibus albidis niti- 

 dis. Pedunciihis brevis, 25 — 35 mm longus. Spica 20 mm longa, 4 — 5-verticillata, 

 interstitiis brevibus. Stylus brevis stigmate ovali, postice in rostellum in fructu ma- 

 ture ssepe persistens protracto. Fructus maturus oblique obovatus 3 mm longus 

 2 mm latus, siccus subcarinatus in vivo verisimiliter dorso rotundatus, rostro brevi 

 apicali v. subapicali. — Fig. 13. 



Anatomy of the stem and leaves: The central cylinder and endodermis of the 

 stem chiefly as in the precedent species, yet the lateral bundles are often reduced 

 so that the original three bundles fuse into one single bundle by which the stele 



becomes four-bundled. The epi- 

 dermis consists of very long and 

 narrow cells, about ten times as 

 long as the width. Inside it is co- 

 vered with a single stratum of cells 

 wherein occasionally occur faint- 

 er bast-bundles, peculiar to this 

 species, though a tendency hereto 

 is observed also in P. vaginatus. 

 In the lacunar part, besides, there 

 is a circle of about 10 — 15 strands, 

 or fewer in very thin stems, some- 

 times an indication of a second 

 circle. The epidermis of the leaf 

 consists of small cubic cells just 

 as in all the other species of the 

 subgenus. The arrangement of 

 the lacunar system does not dif- 

 fer essentially from that of P. 

 vaginatus as a comparison of the 

 two figures (12 ^ and 13 D) will 

 show. Three vascular bundles 

 occur, a median one forming the 

 midrib and two lateral ones 

 nearer to the borders separated from the marginal epidermis by 4 — 5 cell-strata, in the 

 broader leaves. In the very border towards the upper surface either immediately 

 up to the epidermis or separated from it by a single cell-layer there appears a very 

 strong bastcell-bundle, and subepidemally in the upper surface 2 — 3 and in the 

 lower surface 3—4 strong bast-bnndles. 



It is this plant that has at least in some degree, for instance respecting some 

 measure statements, influenced the description of P. famiricus. I am induced to 

 think so, as in the Museums it is mistaken by Baagoe himself for the Pamir plant 

 of Paulsen, and the author has expressly reckoned the plant collected by Robo- 

 ROWSKY in 1894 in Kuen-Luen, which is P. recurvatus m., to his P. famiricus. 



Fig. 13. P. reo«rt'rt/((s Hag-str., ^, Transverse section of the stem, middle 

 part, anatomical diagram, Y*. B, Longitndinal section of the stem-epidermis, 

 ^Y*. C, Transverse section of a narrow leaf, "y*. Z>, Transverse section of a 

 stem-leaf, middle part, showing the lacunar system; three vascular bundles, 

 ft, h-h; two strong marginal bast bundles, and seven strong supei-ficial ones, 

 Y'- ep, - epidermis, hp, pseudo-hypoderma, in the stem one-layered, in the 

 leaf two-layered, ?, lacuna;, x, xylem canals, end, endodermis, cc, stele. Vas- 

 cular bundles hatched. * Eventually occurring subepidermal bast bundles. 



