38 



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



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sed validae, persistentes semper fissae badeo-virides, ut ligulse marginibus albidis niti- 

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

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

 turo saepe persistens protracto. Fruetus 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- 

 demi is 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 tendenc)' hereto 

 is observed also in P. vaginaius. 

 In the lacunar part, besides, there 

 is a cirele of about 10 — 15 strands, 

 or fewer in very thin stems, some- 

 times an indication of a second 

 cirele. 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 E and 13 D) will 

 show. Three vase alar bundles 

 occur, a median one forming the 

 midrib and two lateral ones 

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

 broader leaves. In the very börder towards the upper surface eithcr immediatcly 

 up to the epidermis or separated from it by a single cell-laycr thcre appears a very 

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

 lower surface 3—4 strong bast-bundles. 



It is tli is plant that has at least in some degree, for instancc respecting some 

 measure statoments, influenced the description of P. pamiricus. 1 am induced to 

 tliink so, as in the Museums it is mistaken by Baagök himself for the Pamir plant 

 of Paulsed*, and the autlior has expressly reckoncd the plant collected by Robo- 

 BOWSKY in 1894 in Kuen-Luen, which is P. recurvatus m., to his /'. pamirious. 



Fik. IS. /'. recurvatus Haostb., A, Transverse Bection of the atem, middle 

 part, snatomical diagram, ',''• "• Longitndinal section of the stem-epidermis, 

 ",". C, Transverse section of a narrow leaf, ','. />, Transverse section of a 

 Btem-leaf, iuidill»' part. ■ihowing the lacmiar .system; three vascnlar liumllcs, 

 a. ii-h; two strong marginal bast bnndles, and sevin strong saperflcial ones, 

 ','. ep, epidermis, /</-, psendo-hypoderma, in the stem one-layered, in the 

 leai two-layered, /, lacnnaB, ./-, xylem canals, end, endodermis, ee, stele. Vas- 

 cnlar bnndles batched. * Eventnally ocenrring snbepidermal bast bundles. 



