14 HISTORY OF BRITISH FERNS. 



and the stalk, which latter is often 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 compound, 

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

 the principal one, the latter is called the primary rachis, and 

 the former the secondary rachis. Eew of our native spe- 

 cies are so highly compound as to possess more than a 

 secondary rachis. 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 very constant in the different species or varieties, and 

 hence they sometimes afford good marks of recognition. 

 Whenever they are produced along the rachis, as well as 

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

 become gradually smaller upwards. 



