28 



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



apice saepe recurv T ata, caulina omnia aequilata, 50 X 0,8 — 1 mm, vaginis 15 mm (summis 

 8 mm) longis, ramea angustiora (0,tö mm), superne paulo longiora, vaginis 20 mm 

 longis. Vagince badeo-marginatae juniores integrse ligulis membranaceis 5 — 8 mm 

 longis. Pedunculus brevis (sub anthesi); spica florens brevis (10 mm) 8-flora, floribus 

 minoribus. Pollen ovale magnitudine media. Stylus brevis, stigmate humili, postice 

 in rostrum breve protracto; fruetus non visus. — Fig. 8. 



Anatomy of the stem: Epidermis-cells elongated and rather wide, almost of the 

 same width as the bark-cells supporting it (hypoderma). Endodermis-cells almost 

 insensibly thickened (faint «-cells). The strands of the cortex and the central cylinder 

 as in P. filiformis, from which the anatomy but little differs. The leaf-anatomy 

 also corresponds nearly to that species. Consequently there are two rows of larger 

 b 



= b 



Fi^'. 8. /'. rotlratitt Hagstb. A, Apex of a atem-leaf, '," ; Ii Apex of a branch-leaf, y, tho cross-liaea represent i lie bottoma 

 of the lacnnaa, a, b, See Cl C, Tranaverse-section of a leaf (middle part); a, b, vaacnlar bundits (nerres), T ,°; /', Pistil from 



tbe side, *f; K, Stigma (niore enlargeil) aeen from abovc. 



lacunaj on each side of the small lacunae round the mid-bundle. Seldom someone 

 or other of these greater lacuna3 is longitudinally divided into two (fig. 8, C, to the 

 right!). Towards the leaf-apex the channel-bottoms are scarcely visible outside. The 

 marginal nerves run subepidermally only a couple of cell-layers from the epidermis, 

 and join the mid-bundle quite in the utmost tip (fig. 8, A, B). 



This description is made after a single little flowering specimen and, of course, 

 t lic statement of the length of the pedunele, spike and of the whole plant wants to 

 be completed by further researches. Nevertheless it is even without fruit easily re- 

 cognizablc from the slightly recurved leaf-apex, that in its form much reminds of 

 /\ pectinatU8, and from the stigma protracted backwards in a little beak as in P. 

 recurvatus m., thus combining in an interesting way different groups of the subgenus 

 Coleogeton. The connate sheaths, the ramifioation and other oharactera yc\ show its 

 close relation to /'. filiformis, the group of which it completes by the acute leaves, 

 wheieas the other species have obtuse leaves. 



Distribution, Asia. Mongolia bor. Desertum a Thian Schan boream versus, 

 1877, Potanin (hb. Stockholm.). 



