OP NAIAS GRAMINEAj VAR. DRLILEI. 55 



internal tunic which contains the pollen separates itself 

 from the external raembranCj but, instead of its emerging 

 through the summit of the beak of the perianth, it is 

 thrust through a rupture in the side. 



In A^. graminea the external membrane closely invests 

 the inner membrane, but it is not projected 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 florae ger- 

 manicse^ of Nees ab Esenbeck, show a globose pollen for 

 Naias minor {Caulinia fragilis) in situ, and for Naias major 

 in separate grains (see PI. VI. fig. 19), and in his diagnosis 

 of the genus {Caulinia) 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 plan- 

 tarum^ of Bentham and Hooker^ vol. iii. p. 10 18, viz. 

 " pollen globosum.-'^ In the ' Compendio della Flora 

 Italiana^ of Cesati, Passerini, and Gibelli, part i, p. 204, 

 tab. xxvii. fig. i, the pollen of N. major is elliptico-cylin- 

 drical, like a grain of rice, say from two to three times 

 longer than broad (see PL VI. fig. 26) . In the ' Flora 

 Danica,' plate 212 1, the pollen of Najas marina {Caulinia 

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

 broad. 



This divergence of form in the pollen-grain of Naias 

 major suggests, at first sight, inaccuracy of observation 



