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



dotted lines. Its somewhat broad basal portion with disposition for boss-shaped out- 

 growths is a characteristic of this species. The fruit occurs, besides, with long 

 rostrum as well as short-beaked. 



On the 'inocle of prolongation and growth of the stem etc., see under P. pan- 

 ormitanus! 



Many forms described as ipusillus^ -varieties are not at all varieties of this 

 species but of a hybridous origin. Different narrow-leaved forms they have called 

 »pusillus» without paying attention to their true characteristic qualities, and the 

 limits of this species have been very vague in the literature. 



Var. a major M. & K. (ap. Rohl., Deutschl. Fl. 1823, 857) must be kept as main- 

 form. Concerning P. pus. a major Fries, see under mucronatus! Fischer puts up as 

 main- form his a mucronatus which to me seems to be identical with a major M. & K. 

 Kindred forms are vulgaris Fries, Nov. Fl. Suec, the short-leaved brevifolius Meyer 

 (AscHS. et Graebner, Syn.), further a form endowed with floating leaves, ligulifolius 

 Fischer, Bayer. Pot., and the form with very short internodes and of small growth 

 that MoRONG (Najad.) has called polyphyllus. 



P. pusillus V. ajricanus Bennett is at least pro (maxima) parte in my opinion 

 a form of P. panormitanus Biv. Of a hybrid origin are, no doubt, the varr. capi- 

 tatus, elongatus, acuminatus and Sturrockii (see above, all established by Ar. Bennett!). 

 Var. rigidus Ar. Benn., to judge from the description, is probably a form of P. 

 panormitanus. Var. squarrosus Asch. & Graebn. seems to be a bastard, for which 

 also the single occurrence speaks. The same seems to be the case with the forms 

 spathaceus and retifolius, established by Fischer. 



The form with the narrowest leaves (0,5 mm) is v. teiiuissimus M. & K. The 

 description of the form does not suggest anything but true pusillus. Fischer is 

 of the opinion that this form also contains P. panormitanus p minor, wherefore he 

 has given a new name: cuspidalus (1. c. p. 116). 



I have seen two new forms of this narrow-leaved var. 



f. pygmseus n. f. — Planta statura liumili et omnibus partibus deminuta. 



This form is analogous to v. polyphyllus MoR., which has the usual leaf-width, 

 f. pygmoBus is collected in Sweden: Dalecarlia, Hedemora in Brunnsjon in 1875 by 

 Indebbtou (hb. Stockholm., Uppsal. et Lund.) and at Boda, hb. E. Fries (hb. 

 Uppsal.). West-Bothnia, Umea, 1876, by Andersson (hb. Stockholm.) and at Hapa- 

 randa, Porras udde (head-land), 1868, by Krook (hb. Stockholm.). 



f. brevirostris n. f. Planta foliis angustissimis, rostris brevissimis. 



This plant, collected in Nonvay: Stav, Gudbrandsdal, 1868, by Nordstedt 

 (hb. Stockholm., Uppsal., Lund., Gothob.), has been taken for P. gracilis Fr. 



Var. Berclitoldi (Fieb.) Asch. et Graebn., Syn. mitteleur. Fl. 1897, 345, is the 

 form with rather acute leaves of usual width (1 mm ore more) of which Fieber 

 already has established two forms: ramosissimus and simplex. As to P. Berchtoldi 

 p acuminatus Fieb., see pp. 97, 122! The two lateral »nerves» conducting the midrib, 

 mentioned by Fieber as characteristic of this » species*, are formed by the two 



