'kungl. sv. vet. akademiens handlingab. band 55. n:o 5. 13 



xpusillus!> Fryer, 1907, because of the rounded apexes of the submersed leaves, 

 which are extraneous to P. gramineus as well as to mucronatus {Friesii) and pusillus. 

 See the figs. 37, D, 55, A and 102, H—L, and cf. fig. 68, A! 



As above said the anatomical conditions are of a prominent significance and 

 likewise the turios, styles and stigmata and non-adult specimens withouth spikes 

 (and turios), as they sometimes are met with in herbaria, are often or mostly not 

 recognizable, and many a form already distributed as a certain hybrid need be re- 

 considered. 



For every uniform cross-breed, be it a produce of one or more crossings performed 

 at different places I use the term of form. Such nearly like specimens are com- 

 prised into a series signed a, p etc., corresponding to the variations of common spe- 

 cies, an arrangement already used by me in Neuman & Ahlfvengren, Sveriges 

 Flora, 1901. 



Subgenus A. ColeOg'etOll (Reichenb.) Raunki^r. 



Potamogeton Linn. a. Coleogeton Reichenbach, Icones florae Germanicse et Helv. 

 etc. VII, 1845, 10. — Subgenus Coleogeton Raunki^r, De danske Blomsterplanters 

 Naturhistorie I: 1, 1896, 108. 



Caulis teres vel subteres, ramosissimus— ramosus— subsimplex. Folia uni- 

 formia angustissime linearia ± canaliculata submersa, per totam latitudinem lacunis 

 seu canalibus longitudinaliter perfossa, marginibus semper Isevia, semper vagina ta. 

 Spica deflorata interrupta. Stigma papillosum papilHs majoribus. — Caulis, pedun- 

 culus rachisque flexiles, endoderniide instructi. Fasciculi libriformes caulini ± nunie- 

 rosi semper adsunt saltem in parte inferiore caulis. — Hybernacula (turiones) sub- 

 terranea i.e. in rhizomate affixa. Ex gemmis foliorum jloralium superior est debilior. 

 Pollinatio per aquam. 



Reichenbach, as already Mertens & Koch, equals a. Coleogeton with h. Chloe- 

 geton and c. Antiphyllogeton etc. Raunki^r in his Anatomical Potamogeton-Studies, 

 1903, 261, refers his P. Robbinsii-grouj) to the subgenus Coleogeton for the sake of 

 the sheaths, but this group associates naturally with the subgenus Eupotamogeton. 



The subgenus may be divided into two sections : Connati and Convoluti. 



Sectio I. Connati Hagstr. 



Folia fragiliora, fasciculis libriformibus carentia, plerumque trinervia, nervis 

 ut solet tenuibus, lateralibus subepidermaHter in marginibus sitis. Vagince badeo- 

 marginatse, juniores integrse, hoc est in parte inferiore marginibus connatse, plicatse. 

 — Fasciculi libriformes corticales pauci. — Pollinatio probabiliter in omnibus sub 

 aqua locum habet. 



To this section belong species generally of slender growth and poor in mecha- 

 nical tissue in stem and leaves. Nor do any other anatomical facts afford any more 



