THE PTERIDOPHYTES 285 
365. Discussion. — The life history of a fern differs in a 
striking way from that of a liverwort or moss. Ascending 
Fic. 207. Diagram of Life History of a Fern. 
An, antheridium; Ar, archegonium; s, sperm, e, egg-cell; e’, egg. 
from the lower forms of plant life to the higher ones, it is 
only when the ferns are reached that alternation of genera- 
tions is shown in its most complete form. By this term a 
£99 & 
vA Sperm 
oe Kaun 
Pro 
A. Young 
gy Prothallium 
Fig. 208. Illustrated Life History of a Fern. 
(The young fern-plant is Onoclea, Fig. 209.) 
process of reproduction is meant in which the offspring 
resemble closely not the parent but the grandparent, as 
