56 



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



P. Maackianns Ar. Benxet. 



Xotes on Potamogeton, — in The Journ. of Bot. 1904, 74. — P. semdaius 

 Regel et Maack, in Regel, Tent. Fl. Ussur. 1861, 153. — P. Robbinsii Oakes var. 

 japonicus Ar. Benn. Notes on Japan. Potamog. in Bull. de 1'Herbier Boiss. 1896, 

 546, 549 



Dr 



subsectionem 

 ex cl. A. Ben- 

 prope P. Rob- 



Nevertheless 

 P. obiusifolius 



- Fig. 20, D, E, F. 



P. Graebner in his Potamogeton monograph (1907 p. 108) says, »Af- 



finitas speciei mihi valde dubia est; 

 probabiliter melius 

 propriam constituit ; 

 nett in litt. melius 

 binsii ponenda est.» 

 he puts it near to 

 M. & K. The opinion of Ar. Ben- 

 nett, however, is quite correct, 

 since the species presents the most 

 obvious resemblance to P. Robbinsii, 

 both morphologically and anatomi- 

 cally. To the above stated com- 

 mon characters \ve add: The ana- 

 tomical diagram of the stem is the 

 same, except that the interlacunar 

 strands are absent and the lateral 

 groups of bundles in the stele more 

 reduced. B ut the endodermis is 

 entirely alike in both species. In 

 the peduncle P. Maackianus has a 

 circle of subepidennal strands and 

 besides more vascular- and bast- 

 bundles (fig. 20, F). On the con- 

 trary, the number of the schleren- 

 chymatous strands of the leaf is 

 considerably Limited. To the mor- 

 phologic differonces belongs, among 

 others, that the leaves are of the same width throughout their whole length, the top 

 abruptly cuspidato forming a broad, obtuse apox, the denticulation abating towards 

 the base, that fche xtau is compressed but scarcely bicanaliculate, the cross-out f orm 

 of the pidande oval or oblong etc. Fruit seldom seen. 



Distribution. Japan, Hakone. Siebold it. sec ls;»i» (>:} (hb. Stockholm.). 

 The species obviously has its distribution area in East-Asia: Japan, Corea and adja- 

 cenl districts, thus constituting, by its near affinity with the foregoing species. an 

 interesting combining link of the floras of both sides of (lie Pacific. 



1'iK. 20, .1, /■'. C, V Bobbituii <)\ki>. A, Leaf, X 2,5; Ii, Top of a loaf, 

 '•','; C Transveree section <>( pedanele, Bhowing the ahape and the dispo- 

 sition of the bundles, '-','"• /'. /•-', /■', /'. Maackianus J1i:nn. />, Leaf, X '2,:>; 

 /•.', Top "i a k.if, ','; /■', Cross sc.-t i->ii of pedmi^le, showing the snbepi- 

 dermal stranda [tir] and laeanar bnndles (batched), ',"; m, »', n", sW = 

 Kg. 19. 



