10 BRITISH FERNS. 



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 extensively adopted for culture 

 where ornamental effect is an object. 



The fronds of Ferns consist of two parts the leafy por- 

 tion j and the stalk, which fatter is called the stipes. The 

 continuation of the stalk, in the form of a rib extending 

 through the leafy portion, and becoming branched when the 

 frond is divided, is called the rachis. If the frond is com- 



Eound, that is, divided, so that there is another set of ribs 

 esides the principal one, the latter is called the primary 

 rachis, and the former the secondary rcichis. In but few 

 cases are our native species more highly compound than 

 this. In practice, when the outline or division of the frond 

 is mentioned, it is generally the leafy portion only that is 

 referred to, exclusive of the stipes. 



The stipes is generally furnished more or less with mem- 

 branous scales, which are sometimes few and confined to the 

 base, and at other times continued along the rachis. Some- 

 times these scales, which are generally brown, are large and 

 so numerous that the parts on which they are situated acquire 

 a shaggy appearance. The form of the scales, as well as 

 their number and position and even colour, is found to be 

 tolerably constant in the different species or varieties, and 

 hence they sometimes afford marks of recognition. When- 

 ever they are produced along the rachis, as well as on the 

 stipes, they are invariably largest at the base, and become 

 gradually smaller upwards. 



In some species the leafy portion of the frond is undi- 

 vided, that is to say, the margins are not scalloped or cut 

 away at all : an example of this occurs in the common Hart's- 

 tongue. More commonly, however, the margin is more or 

 less divided. 



The simplest mode of division is that where the margin 

 of the frond is deeply divided or scalloped out at short in- 

 tervals, the incision extending inwards nearly to the rachis, 

 but not reaching it : this slightly divided form is called pin- 

 natifid. 



The fronds are sometimes divided down to the rachis, 

 which is, as it were, quite bared of the contiguous leafy ex- 

 panded portion, and when this occurs, the frond is said to be 

 pinnate ; and in this case, each of the distinct leaf-like divi- 

 sions is called a pinna. When these pinnae are divided again 

 upon precisely the same plan, the frond becomes bipinnate, 



