xvii] VEGETATIVE REPRODUCTION 225 



noted that certain Cryptogams (e.g. Riccia, Fontinalis and Pilu- 

 lariay) behave Hke the Flowering Plants we have cited, in not 

 producing sexual organs in deep or rapidly flowing water, 

 while the replacement of sporangia by young plantlets has been 

 recorded in the case of certain examples of Isoetes lacustris and 

 /. echinos-pora^^ which grew at a considerable depth in one of the 



Fig. 148. Caldesia parnassifolia, 

 (Bassi) Pari, forma nutans. A deep 

 water plant which has developed 

 axes bearing turions (T-^ and T^) 

 in place of inflorescences. (Re- 

 duced.) [After Gliick, H. (1905), 

 Wasser- und Sumpfgewachse, Bd. i, 

 PI. IV, fig. 25.] 



A 



Fig. 149. Caldesia parnassifolia, 

 (Bassi) Pari. A, 'turion inflor- 

 escence' from a plant growing in 

 water 50 to 60 cms. deep. (Re- 

 duced.) B, turion which germinated 

 in water 50 cms. deep. (Slightly 

 enlarged.) [After Gliick, H. (1905), 

 Wasser- und Sumpfgewachse, Bd. i, 

 PI. IV, figs. 27 a and 28.] 



lakes of the Vosges country. The occurrence of tubers in lieu 

 of flowers in Castalia Lotus^ can be paralleled among such 

 terrestrial plants as Polygonum viviparum^ but aquatic condi- 

 tions seem particularly to favour a general tendency to replace- 

 ment of sexual by vegetative reproduction. 



1 Schenck, H. (1885). 2 Goebel, K. (1879). 



3 Barber, C. A. (1889) ; see Fig. 19, p. 37. 



A. W. P. 



15 



