317 



A 



B 







alterniflorum and i¥. verticillatum. The plants examined were 

 taken in July and August. 



Both species flower in July -September, M, spicatum taken 

 by Vanhoffen at 70°30' N. L. on July 18 (Abromeit 1899 p. 12). 



MyriophyUum is monoecious. Warming (1886 p. 116) gives 

 M. a. and M. spic. among the anemophilous plants of Green- 

 land (cf. Kndth 1898 p. 309). So far as I know, water-pollina- 

 tion has not been noted for these two species as for M. verti- 

 cillatum (Ludwig 1881 p. 10). Abromeit (1. c.) observed distinct 

 protogyny in M. spi- 

 catum^ in the Umanak 

 Fjord district, but 

 further, that the pol- 

 len is emptied already 

 in half-opened c? flo- 

 wers. Schindler ( 1 905 

 p. 14l remarks, that 

 the lowermost, first 

 opened flowers of 

 several MyriophyUum 

 species are wholly 

 female. 



The pollen grains 

 of M. alterniflorum 

 (fig. 9); both in arctic and Danish specimens, differ from those 

 of M. spicatum and M. verticillatum as described and figured 

 by MoHL (1834 p. 331). The pores of the pollen, usually 4, are 

 placed 2 near one another at the one pole, 2 at the other, and 

 not with the same distance between all 4 as in the other species. 

 2, 3 and 5 may also occur; 6 may also be found in M. spicatmn, 

 just as we sometimes see transitional forms with regard to the 

 distance between the pores. 



The outgrowths mentioned in Schin-dler's description (1905 

 p. 94) as occurring on the ovary of M. a., give with vanillin 

 XXXVI. 21 



C i> 



Fig. 9. MyriophyUum. Pollen {X ca. 100). 



A and B M. alterniflorum DC. A Danish, B Arctic. C M. 

 verticillatum L. D M. spicatum L. 



