204 



THE PLANT WORLD 



which produces (7) and . . 



(9) grows into a leafy 



(10) spores. 



. . . . (8). After fertilization an 

 moss plant which produces 



PROBLEM IX. WHAT IS THE LIFE HISTORY OF A FERN 



PLANT? 



The pteridophytes are a group which, when the world was 

 younger, played a very important part in the vegetation on the 

 earth. Some coal is made very largely from their bodies. They 

 have true roots, stems, and leaves, but reproduce like the mosses, 

 by forming spores. 



Life history of a fern. The common fern begins life as a spore. 

 This germinates into a tiny heart-shaped body called a pro- 





■Stbofliui 



The life history of a fern, (it Adult plant, (2) a leaflet showing sori or groups 

 of spore cases, (3^ a section through a sorus, (41 a spore case opening, (5) a 

 spore which germinates into (6) a prothallium which in turn produces organs 

 containing (7) sperms and (8) eggs. When an egg is fertilized it gives rise to 

 (9) a new fern plant. 



thallium which contains sex organs holding sperm and egg cells. 

 This is called the gametophyte generation of the plant because 



