238 



J. O. HAGSTROM, CRITICAL RESEARCHES 0>* THE ruTAMOGETO.NS. 



Fig. 111. /'. lucens L, form with 

 Kiticillate leaves. Anatomical diagram of 

 the vascular bundles of the central cvlin- 

 der V- 



Lastly I will remark that I haveseen a vcrticillatus- 

 form of P. lucens from the Nibså in Denmark with fonr 

 leaves placed in a verticil round the st em. In the 

 central cylinder it exhibits four free large vascular 

 bundles running in the centre, and three peripheric oncs 

 belonging to lowest leaf next above, besides which the 

 traces of the other three leaves are crowded in a separate 

 quarter. The figure 111 gives an idea of the compli- 

 cated arrangement of the bundles. For the rest the 

 anatomical conditions are normal. 



P. lucens L. x iiatans L. 



(P. sterilis n. nom. — P. iiatans X lucens ex Beebv, On P. jluitans Roth in 

 The Journ. Bot., 1890, 204. — P. lucens X natans (P. jluitans Auctt.) ex Raunki.kk, 

 Danske Blomsterpl., I, 1896, 97. — P. Noltei Fischer, vide infra!). 



Canlis ssepissime altus robustus ramosus. Folia subm.±longe petiolata inte- 

 gerrima laminis longis anguste — angustissime lanceolatis; suprema saepissime ± coriacea 

 petiolis lamina typice brevioribus, basi in petiolum ± angustata, conspicue et ± acute 

 cuspidata. Ligulce 5 — 9 (15) cm longae bicarinata? ± persistentes. Pollen semper sterile. 



The English authors Ar. Bennett and A. Fryer have used the name P. 

 jluitans of this hybrid. F. Buchenau, Flora nordwestd. Tiefeb. 1894, also considers 

 part of the » jluitans* -forms to be the hybrid lucens X natans. Of the earlier authors 

 E. F. Nolte and E. Fries likewise have evidently had this hybrid in view when 

 mentioning P. jluitans. S. Liljeblad, again, in Utkast till Svensk Flora, 1798, 

 describes the hybrid P. gramineus X natans under the name jluitans; but according 

 to J. E. Smith, Flora britannica, 3. 1391, P. jluitans is supposed to be P. alpinus 

 Balbis, and in Pursii's Flora Americae septentr. 1814, it is obviously about P. 

 NuttaUU. — G. Fischer has first signed this hybrid with a proper name: *P. Rothii 

 Bennett» (which name Bennett has not distributed) låter rejected for the name 

 P. Noltei (Mitteil. n:o 32 der Bayer. Bot. Ges. 1904, 375) which name Bennett 

 reallv used in 1890 of P. gracilis Fr. To Fischer is »der fertile und der sterile 

 P. jluitans doch auf einen gemeinsamen Typus öder Stamm zuriickzufuhren» (G. 

 FlSOH., Bemerkungen etc. 1914), and consequently he writes: I', jluitans proles I 

 {=P. nodosus Poir.)» and i proles II Paunkiari , with which hc includes the var. 

 typicuå Boe, the var. sublucens Bok, and »/'. Harzii*, of which all, see below ! 



Like its originators P, sterilis is usually branched and of high growth but va- 

 rics otherwise in Imbit espeoially as to its upper nalf, wbere it now approaches to /'. 

 natans with abundant, now to /'. lucens with very faint evolution of f loating leaves. 

 Usually it keeps a medium between the two, then having one or a couple of rather 

 distinct Bubcoriaceous leaves, which always are t hinner 1 lian in /'. natans. In part 



