18 



ON NAIAS GEAMINEA DEL., VAR. DELILEI MAGNUS. 



fig. 23 ; a vertical section of N. minor in fig. 27 ; 

 and a vertical section of N. major, in fig. 21. 



The membrane which invests the anther is 

 formed of close-ranked, elongate, translucent 

 cells, six to twelve times as long as broad, and 

 tinged with a beautiful rose-colour; the super- 

 position of this rosy membrane over the lemon- 

 coloured pollen of the anther gives the flower a 

 tawny-orange appearance, which readily attracts 

 notice, even without the aid of a lens. The cells 

 which compose the ridges in the upper half of 

 the flower are larger and broader than those of 

 the rest of the membrane. 



Eobert Brown's N. tenuifolia has considerable 

 affinity with the Manchester plant, but, inde- 

 pendent of other differences, the anther is very 

 dissimilar on account of its external tunic termi- 

 nating in a narrow elongate beak, which bears a 

 number of brown spiny teeth at its free end (see 

 fig. 15, Plate 251). At the period of dehiscence 

 the internal tunic which contains the pollen 

 separates itself from the external membrane, but, 

 instead of its emerging through the summit of 

 the beak of the perianth, it is thrust through a 

 rupture -in the side. 



In N. graminea the external membrane closely 

 invests the inner membrane, but it is not pro- 

 jected beyond it in the form of a beak ; and 

 I have not seen a vestige of a brown spiny cell 

 on any portion of the male flower. 



XII.— The Pollen. 



The pollen of the various species of Naias does not seem to 

 have been much noticed by observers. Magnus does not allude to 

 it, nor give any figures of pollen-grains for any of the species ; and 

 contradictory statements are made by some authors. Thus the 

 drawings of Braun, engraved in fasc. x., plate i., of the ' Genera 

 plantarum floras germanicse ' of Nees ab Esenbeck, show a globose 

 pollen for Naias minor (Gaulinia fragilis) in situ, and for Naias major 

 in separate grains (see PI. 251, fig. 19), and in his diagnosis of the 

 genus (Gaulinia) he specifies " pollen globosum, magnum." This 

 statement seems to be the foundation for the similar statement in 

 the works of later authors, one of the most recent being given in 

 the ' Genera plantarum ' of Bentham and Hooker, vol. iii.,p. 1018, 

 viz., " pollen globosum." In the ' Compendio della Flora Italiana ' 

 of Cesati, Passerini, and Gibelli, part 1, p. 204, tab. xxvii., fig. 1, 

 the pollen of N. major is elliptico-cylindrical like a grain of rice, 

 say from two to three times longer than broad (see PI. 251, fig. 26). 

 In the ' Flora Danica,' Plate 2121, the pollen of Najas marina 

 (Caulinia fragilis) is of an elliptical form, not quite twice as long as 

 broad. 



Fia. 78. 



