134 
HISTORY OF BRITISH FERNS. 
Asplenium Ruta-muraria, Linnwus. 
The Rue-leaved Spleenwoi't , or Wall Rue. 
(Plate XIII. fig. 1.) 
A very diminutive, and not very attractive Fern, occur¬ 
ring abundantly on old walls, often in such situations 
little more than an inch high. It grows in tufts, insinu¬ 
ating its wiry roots, as is the case with all the mural 
species, into the crevices and joints of the masonry, and is 
not easily removed from such places in a condition suitable 
for planting. 
The fronds are numerous, of a glaucous-green, varying 
between one and six inches long, with a stipes about half 
the entire length, the leafy part usually triangular in out¬ 
line, and bipinnate. The pinnae are alternate, with rhom- 
boidal, or roundish-ovate, or obovate pinnules, sometimes 
wedge-shaped, with the apex abruptly cut off. The more 
luxuriant fronds are once more divided, so as to become 
almost tripinnate, the pinnules being deeply pinnatifid, 
and the lobes formed like the ordinary pinnules. When 
the plants are quite young, the fronds are simple and 
roundish kidney-shaped. At a later stage of development 
they are occasionally only once pinnate, with pinnatifid 
