xv] ORIGIN OF AQUATIC HABIT 203 



amphibious plants were not originally gifted with any special 

 aptitude for aquatic life, but that they have gradually acquired, 

 and passed on to their descendants, the capacity for reacting 

 in an advantageous way to the stimuli of an aquatic environment, 

 and that we are thus dealing with a case of the inheritance of 

 acquired characteristics. But the second alternative, which 

 appears to the present writer to have most in its favour, is that, 

 in general, those species which are capable of a suitable response 

 to aquatic conditions have already been sifted out by nature, 

 and now inhabit situations where such conditions, at least 

 occasionally, arise; or, in other words, that the various species 

 of flowering plants were all endowed, from the first moment 

 of their appearance, with different constitutions which gave 

 them varying degrees of capacity for the adoption of water life; 

 and that their habitats have been determined by this capacity 

 and not vice versa 1 . 



A B 



FIG. 134. Ranunculus Flammula, L. 

 A, form with floating leaves. B.land 

 form. (Reduced.) [ After Gliick, H. 

 (1911), Wasser-undSumpfgewachse, 

 Bd. in, Figs. 84 and 85, p. 494.] 



FIG. 1 35. Ranunculus Flammula, 'L. 

 Submerged form. The short up- 

 right stem replaces the inflor- 

 escence. (Reduced.) [After Gliick, 

 H. (1911), Wasser- und Sumpfge- 

 wachse, Bd. in, Fig. 86, p. 496.] 



J 



1 See Footnote i, p. 162. 



