The Fern Alliance 



One period of the life of a fern is that known as the 

 prothalHum. In some ferns (Schizaea bifida and Tricho- 

 manes) the prothallium is very Hke an alga and pro- 

 bably lives in water, but in most it is a little flat green 

 and fleshy body which flourishes on continually damp 

 soil.^ 



So Von Wettstein gives a neat little figure showing 

 the way in which land plants developed out of what 

 was once a purely water-flora. 



This point has been elaborated in an important work 

 by Professor Bower.^ 



The algae and fungi are essentially water-plants, and 

 the process of fertilisation is performed in water. The 

 little free-swimming sperm cell or male cell swims to 

 the egg cell and effects fertilisation under water. Then 

 the egg cell begins to develop. In many algae and 

 fungi it does not at once form a new alga, but grows, 

 dividing many times, so as to form a number of cells. 

 Some of these are the spores which will produce the new 

 alga or fungus, but others may never become spores at 

 all. Some cells will form a sort of shell or envelope to 

 hold the spores, and others may become creeping fila- 

 ments which attack the branches of the parent alga and 

 absorb food material from them {e.g. Florideae). 



This stage in the life-history from the egg to the 

 spore may be called the spore-plant. This spore grows 

 into what we call the alga, which produces the sperm 

 and egg cells. In mosses the sperm cell also reaches 

 the egg cell by swimming, for during the life of most 

 mosses (especially in February to March in England), 

 moss-tufts are often covered with rain water. The egg 

 cell in mosses, when fertilised, grows and forms the 

 elegant little stalk which ends above in a small capsule, 

 from which the spores are distributed. The base of the 

 stalk extracts food material from the mother moss, and 



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