THE LIFE HISTORY OF FERNS n 



change of environment, however, involves more than a mere 

 change of form and texture. The foliage in the water requires no 

 support ; it simply floats, and it is probable that at first the 



l r 'g' 3' — Developed Prothallus, Antheridia, and Antherozoids. 



modified land plants got over this difficulty by being merely adherent 

 to surfaces, as is still the case with our Marchantias, or Liverworts, 

 and Lichens of to-day. The next thing, however, was the evolution 



