THE STRUCTURE OE FERNS. 13 



Even in the few species which are natives of Britain, this 

 variety of size and form is very obvious, some kinds not 

 being more than two or three inches, others five to six feet 

 or more in height, some quite simple, and others cut 

 into innumerable small segments. There is much variety 

 of texture too : some being thin and delicate, almost trans- 

 parent, others thick and leathery, and some perfectly rigid ; 

 some are pale green, some are deep green, some are blue- 

 green, some dark brownish, scarcely green at all ; some are 

 smooth and shining, others opake, and some few are 

 covered with hair-like scales. 



The duration of the fronds of many species is compara- 

 tively short : they come up in spring, and in some cases 

 the earliest of them do not last till autumn, in others they 

 continue until touched by frost, from which the more 

 robust of them shrink, even as the tender sorts do from 

 drought as well as frost. Others are much more durable, 

 and the plants, if in a moderately sheltered situation, 

 become evergreen. These latter should be most ex- 

 tensively adopted for culture where ornamental effect is an 

 object. We shall point out these peculiarities as we de- 

 scribe the different species. 



The fronds of Perns consist of two parts the leafy portion; 



