82 



J. O. HAGSTROM, CR1TICAL RESEARCHES ON THE FOTAMOGETONS. 



are either quite wanting or present 



in a very slight number. The 



crosscut-form of the central stele 



is rliomboid, which results from 



the median bundles running more 



separat ely than in general and 



the lateral ones being considerably 



reduced both in number and size, 



the stele thus presenting a four- 



bundled diagram. The leaves taper 



more abruptly into an apex, less 



acute by far than in P. polygonus. 



The leaf is through its whole width and up to the very 



top intersected or replenished with narrow channels, the 



crosswalls of which are rather approximate, which 



makes it appear reticulate under the lens. Two vascular 



bundles run on either side of the main-rib and, between 



them, thin bast-bundles nearly as in the foregoing species, 



but the börder-strand is considerably weaker. Ligules 



more durable, their front-field is 12 — 15 (IT)-fibrous. 



It should be observed, that my researches are made 

 on young shoots from a creeping rhizome, the only 

 materials hitherto accessible to me. Spike-bearing indivi- 

 duals may have the interlacunar sclerenchyma (the ligu- 

 lar bundles) a little more developed. 



The species is figured in Graebner, Potamog. ap. 

 Engler, Pflanzenreich IV, 11, 1907, 105, f. 25 A (habit- 

 figure); B, fruit, seems to me to be a polygonus-iruit, 

 cfr. Schumann, fruit 1,5 mm long etc. 1. c ! 



Distribution. Brazil, Prov. Rio de Janeiro, Serra 

 ä, Z&2J. 5^7X^*2 do Itatiaia > 2 > 460 m - s - m- ° 2 ' DusÉ * ( hb - Stockholm.). 



middle, V, showing the lacnnar system (?) _ Leg GLAZIOU, N. 6721; det. ScHUM. (llb. Hailll.). 



aml the bast-bnndles; slr, marginal strand; 

 m, »', nervea \.i-,.-nlar bundles); B, Pi.->til ; 

 a, lateral vn w, /,, \i ntral view, Y'; G, Trani- 

 \ 'ni; si-1'tifin ni the rent nil axis Of the Btom, 



showing the bnndles and their eham 



— I> /•', P. XJlti Sciiiim. D, Transverse 

 section "i stem, showing the arrangemeni 

 of the laonnai system, the eabepidermal 

 Stranda ttl , and thl vasealar bundles of 

 the centra] oylinder [ee), X occasionallj 

 oconrring interlaonnar bnndle, 'V'; E, Top 

 "i :i stem-leaf, ',■'; /'. Transverse section of 

 tin^ leaf, at the middle, /", »', ttr, as m 

 I 



m- 



Subsectio 11. Oxyphylli Hagste. 



Caulis ± compressus internodiis elongatis, nodis 

 biglandulosis. Fulia linearia multinervia acuta vel acute 

 cuspidata basi ± rotundata. Ligulce fissse, multinervisB, 

 apice rotundata'. Pistill iim stylo brevi stigmale parvo. 

 Fruetus ovoidei leviter compressi (/\ oxyphyll.). 

 Thia group occupies an intermediate position between t hc Polygoni and the 

 /'//s/7//. It is like the Latter as regards the styles and stigmas, but differj by the 



