80 FERNS 



spores. When the spores are mature the sporangium loses 

 its moisture, the outer walls of the cells of the annulus bend 

 inward, the sporangium is split open and the spores are carried 

 away by the currents of the air. 



Reproduction. The two types of reproduction common 

 to the ferns are (1) asexual reproduction and (2) sexual 

 reproduction. 



1. Asexual Reproduction is brought about in one of four 

 ways: 



(a) By division of the rhizome. 

 (6) By the formation of bulbils. 



(c) By the formation of stolons. 



(d) By spore germination. 



(a) By Division of the Rhizome. When the rhizome is 

 divided into two or more parts, each part may develop into 

 a fern. 



(6) By the Formation of Bulbils. In certain species of 

 ferns bulbils or buds form on the surface of the leaf and 

 when they fall to the ground they grow into ferns. 



(c) By the Formation of Stolons. In the so-called walking 

 fern, the tips of the leaves recline on the ground, develop 

 roots and later produce typical fern plants. 



(d) By Spore Germination. The spores produced in the 

 sporangium will, under favorable conditions, develop a 

 slender tube or protonema. This tube produces a branch near 

 the spore, which develops the first rhizoid. The protonema 

 divides and redivides to form a flat green heart-shaped pro- 

 thallus, one cell in thickness. The prothallus bears the 

 sexual reproductive organs. 



2. Sexual Reproduction. The two types of sex organs 

 are similar to those of the liverworts and mosses, namely: 

 antheridia and archegonia. Antheridia grow on the under 

 side and near the point of the prothallus. An antheridium 



