64 



J. O HAOSTROM, CRITICAL RESEARCHES ON THE POTAMOGETONS. 





signed combination: 1) The filiform stem bas not the strongby compressed shape that 

 has P. obiusifolius. The cross-cut form and anatomical diagram (fig. 24, B) evidently 

 is intermediate betvveen P. pusilhts and crispus. Evidence for the latter are the two 

 furrows, the subepidermal strands reduced in number and the bundle-trio (fig. 24, 

 B, tr) of the central stele; for the former, again, the rounded form of the stem 

 and of the central axis, and the few subepidermal bast-bundles. To these decisive 

 facts come (2) the narrow stem-leaves, and (3) the small turios intermediate 



between crispus and pusillus, not 

 between the former and obtusi- 

 folius, the buds of which are 

 larger than those of P. Ben nd ti i, 

 a fact that otherwise ought to 

 be the very inverse. 



The specimens examined are 

 labelled: »Stirling V. Co. 86. 

 Wood Pond: Grangemouth. Aug. 

 24. 1894. R. Kidston & Col. 

 Stirling. A. F. n. 3001» (hb. 

 J. Baagöe). Thus originating 

 from an exceedingly interesting 

 Potamogeton-region of Scotland. 

 — It is not known to me if P. 

 concinnitus Ar. Benn. (crisp. x 

 pus.? ex Ar. Benn.) is the same 

 hybrid as the Stirling plant 

 or not. 



i c/ 



IO/ 



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J^-JCJQ ..-ff : TÄr,. - JO <->£\ A 



Subsectio 7. Compressi 

 (Fries No v.) Hagstr. 



Caulis valde compressus. 



Fig. 24. .1, /'• crispus L., Cross sectiou of the B t em, ','■ ; /'. /'. Ben- -i > i ■ p • • j. 



i ,, ; Oroaa section of the stem, ','•; C, Oross section of P. pttHttu 1'olui angUSte lineana lUteger- 



i. .", and h, Cross Bectiou of P. obtusifoliua, \-. x, intercellnlar ohannels, ,.:,,, „ ,,, 11 lf;,- 10 i.i-i«i l, no ; !.,*„ rr . 

 / Iscnnn rfr, strands; /-.. /'. BennelUi Fbtsb, Top <>i a stemleaf, \. 



tundata, apice aeutissime ouspi- 

 data. LigvloR semper fissse, in spatio intermedio multinervise. Pistillum stylo bre- 

 vissimo, stigmate ovali-oblongo. Fruetus dorso ssepe rugosus. 



This group is characterized by the short style and oval stigmas covering the 

 wholr upper surface of the style. By this it closely joins the Monogyni m. (below), 

 whereas the strongly eompivssed stem unites it with the Criapi. Anatomically it 

 differs from all the COntigUOUS groupa by the strong, marginal, eauline strands being 

 provided with vessels, Fig. 2f> .1, «, D, a. The abundance ol the foliar schlerenchyma 



