CH. vii] THEHORNWORT 85 



and thus comes into contact with the stigmas^. This water- 

 carriage of the pollen is the more striking, since the great 

 majority of aquatic plants show a strong tendency to retain the 

 aerial pollination mechanism of their terrestrial ancestors. 



As regards vegetative structure, the most notable feature of 

 the Hornwort is the entire absence of roots. The radicle 



C B 



Fig. 54. Ceratophyllum demersum, L. A, node bearing two male flowers {^) (En- 

 larged) ; a branch {b) and all the leaves but two (/) have been cut across. B, 3: 

 single male flower on a larger scale; p, perianth of about 12 members; st, stamens. 

 On the left, a stamen is in the act of being squeezed out. C, $ flower; a, showing 

 perianth, style and stigmas ; b, with perianth removed showing ovary. The stigma 

 varies from being single to being sometimes much more deeply bifid than in C. 



[A. A.] 



never develops beyond a rudimentary stage and no adventitious 

 roots are produced. Fig. c,^, p. 86, shows a seedling^ with its re- 

 duced radicle (r). The seed germinates at thebottomof the water, 

 the plantlet rising to the surface when it is about three inches 

 long. The leaves of the first pair (/) are linear and decussate. 



1 Willdenow, C. L. (1806), Dutailly, G. (1892), Roze, E. (1892), 

 Strasburger, E, (1902). 2 Guppy, H. B. (1894I). 



