FERNS, AND THEIR ALLIES. II 



intermediary stage. When fern spores germinate, 

 a kind of filmy green membrane is produced, which 

 cannot be called a leaf; it lies flat upon the soil, 

 adhering by means of delicate rootlets proceeding 

 from its under surface, which, when mature, is lobed, 

 or almost heart-shaped. This delicate "false leaf" 

 is technically called a prothalhis. Its structure and 

 its use is not that of an ordinary leaf, as it is only 

 a temporary expansion upon which the future young 

 fern is to be developed, and to call it a leaf would 

 simply be misleading. When this filmy "prothallus" 

 is matured, two kinds of organs are produced on its 

 under surface, and these represent the male and 

 female principle in the process of fertilization. One 

 kind of organ contains the germ of the future plant, 

 a kind of bud in its rudimentary state ; this may be 

 termed the " germ-cell." The other organ represents 

 the fertilizing principle, and may roughly be designated 

 as a little bag or cell, containing active thread-like 

 bodies, which, when liberated from the cell, move 

 about as though endowed with animal life. When 

 the little bud or germ has reached a proper state of 

 maturity, it protrudes from its cell, and comes into 

 contact with some of these mysterious little active 

 thread-like bodies, and thus the bud is fertilized. 

 Gradually the lively bodies become still and dis- 

 appear, the bud increases in size, the green membrane, 

 or prothallus, disappears also, and nothing is left but 

 the young bud, which begins to put on the appear- 

 ance of a miniature fern plant, develops little fronds, 

 and grows up in the likeness of the parent plant 

 from whence the spores, or seeds, were first taken. 



