i8 HOW TO KNOW THE FERNS 



was shown that the spermatozoids steered a 

 decided course towards the archegonia, but the 

 reason for this has only been comparatively 

 recently explained. At the mouth of the 

 archegonia there is a viscid drop which almost 

 certainly contains chemical substances attrac- 

 tive to the spermatozoids. Although the 

 nature of the substance is not exactly known, 

 it is suggested that this may be malic acid, 

 seeing that experiments have shown that the 

 spermatozoids are attracted to this product 

 when it is artificially introduced. Of course 

 the matter is a difficult one to prove, in that 

 the viscid drop is so minute that it is impossible 

 to determine the nature of the substance which 

 it contains. Malic acid has, however, been 

 discovered to be present in the prothallus as 

 a whole. Although there is quite a competition 

 amongst the spermatozoids as to which shall 

 enter the archegonium, it is likely that only 

 one actually succeeds in entering the egg cell. 

 As a rule, too, in the prothallus only one of 

 the archegonia shows any further signs of 

 development. 



After the fertilization is completed the first 

 happening is the formation of a cell-wall round 

 the ovum. Passing through various stages of 

 growth and subdivision it finally forms the 

 embryo of the young plant. For a while the 

 newly-born Fern relies upon the prothallus for 

 sustenance, but eventually starts an inde- 

 pendent existence. The baby sends down roots 

 into the ground and leaves up into the air, and 

 from thenceforward its development into a 

 mature plant will only be a matter of time. 



The life histories of the Club Mosses have 

 certain points which make them of special 

 interest. In the first place, the manner of 



