THE LIFE OF A FERX. 19 1 



life, they become erratic, and show a disposition to pass beyond 

 the ordinary limitations. Curious examples of tendency to a 

 greater than even their proper large amount of subdivision 

 are occasionally shown in specimens of the lady-fern, which 

 become forked at the extremities not only of the fronds but of 

 the leaflets also. 



The manner in which the fronds divide into lobes, segments, 

 leaflets, and so on, is of course largely dependent upon the 

 character of the veining, which differs widely from that of the 

 flowering plants. In these, the veins are either netted or 

 parallel, but in ferns they are forked, each branch again forking, 

 and so on outward to the margin. This is only partially true 

 of the scale-fern, and not true at all of the adder's-tongue ; 

 but it is the case with all other of our native kinds. 



SCALY SPLEEXWORT OR " RUSTY BACK.'' 



Passing now to the production of the spores, and so com- 

 pleting the cycle of a fern's existence, these appear in cases 

 which spring in some instances from leafless veins or central 

 ribs, but mostly from the veins as they usually occur, and at 

 the back or, in the bristle-fern and filmy-ferns, at the margin 

 of the fronds. The cases grow in clusters which are termed 

 sori, each of which is generally protected by a covering, though 

 in the genus of the polypodies this is entirely absent, the 

 clusters being fully exposed to the diversities of wind and 

 weather. In the protected kinds, the cover assumes vanous 

 forms. The filmy-ferns have it as a tiny cup, enclosing the 

 spore-cases. In the bladder-fern it is like a fairy helmet. 

 The shield-ferns, as their name implies, produce it as a little 

 shield, fastened by its centre. In the buckler-ferns it is 

 kidney-shaped, in the spleenworts long and narrow, and so on. 

 Some kinds can scarcely be credited with the formation of a 

 real cover, but their sori are protected by the turned-down 

 margins of the fronds. In a few sorts, separate fronds are 



