SECT. Tin. 



ASPLENIE&, 



353 



Fig. 62. Athyrium Filix- 

 fcemina. 



commonly a semilunar outline, as in fig. 62; but they 

 are occasionally so much curved as to acquire a horse- 

 shoe form, and more rarely they are 

 linear, and they become at length 

 reflected by the growth of the spo- 

 rangia. In some varieties they are 

 distinct, in others so close as to 

 become eventually confluent and 

 completely cover the surface. The 

 Filix-fcemina is distinguished by 

 the linear junction of the indusium 

 with the frond. It is one of the 

 most variable of all the known 

 ferns, and is remarkably prolific, so that new forms 

 may be raised from the spores. There are a very large 

 number found in this country. 



All the Aspleniese have linear sori attached to the 

 side of the vein, so that they are said to be lateral. The 

 indusium opens on its inward side, and is sometimes 

 ciliated. There are many tropical ferns of this group, 

 but the genus Asplenium, which has representatives in 

 all parts of the world, yields 

 eight or nine species in Great 

 Britain. 



The Asplenium Ruta-mura- 

 ria, or Wall Rue, is an indige- 

 nous mountain plant growing 

 in tufts six or eight inches high 

 in the clefts of the rocks, but 

 has diminished much in size in 

 migrating to the plains, where 

 it is found on old brick walls 

 and outhouses. The fronds 

 are deltoid and bipinnate, the Fig * 63 ' 

 pinnules are wedge-shaped and notched, or toothed, on 

 their upper margin ; their colour is deep green, but in 

 VOL. i. A A 



