16 HISTORY OF BEITISH TEENS. 



The young fronds of the ferns before being developed 

 are arranged in a very curious manner, the rachis being 

 tolled inwards from the point to the base, and in the com- 

 pound sorts the divisions are each again rolled up in a 

 similar way. This arrangement is what is called circinate. 

 All the British species, with two exceptions, are folded up 

 in this way, so that their development consists of an un- 

 rolling of the fronds. The exceptions mentioned, are the 

 Moonwort and the Adders-tongue, in both of which the 

 fronds in the undeveloped state are folded straight. 



The substance of the fronds is traversed by veins vari- 

 ously arranged; in some species forming straight parallel 

 lines, in others joined together like net-work. The manner 

 in which the veins are disposed is called the venation, and 

 the nature of this venation affords useful data in the divi- 

 sion of the ferns into family groups. It is from some 

 determinate part of these veins that the clusters of fructifi- 

 cation "proceed, that part to which they are attached being 

 called the receptacle. A correct appreciation of the con- 

 dition and position of the receptacle with reference to the 

 veins, is of considerable importance in the study of the 

 genera and species that is to say, the individual kinds and 

 the family groups. In some, though few of the native 



