352 



BOTANY OF THE LIVING PLANT 



once to increase its slender store, otherwise it cannot produce gametes, 

 or nourish the resulting germ. Hence the independent vegetative 

 existence of the gametophyte. 



"M^- 



Fig. 295- 

 Nsphrodium psetulo-mas, v. cristata (Cropper) . Drawing by Dr. Lang showing 

 apogamous transition from prothallus to sporophyte, and subsequent aposporous 

 transition to prothallus at the apex and margins of the leaf. 



Further, the difference in biological relation of the two generations 

 to water is very marked. The prothallus, which is semi-aquatic, is the 

 less prominent, and its growth is normally limited in size and duration. 

 The Fern-Plant, which is definitely terrestrial in structure and function, 

 is in the ascendent, and its growth is unhmited in size and in duration. 

 A Fern is like a man with one foot in the water and one on land. But 

 the foot that is on land is more firmly set than the other. 



