112 
RUE-LEAVED SPLEENWORT. 
pinnules are irregularly-toothed. The venation con- 
sists of a series of veins repeatedly forked from the 
base, so that there is no distinct midvein ; the number 
of the venules corresponds with the number of 
marginal teeth. Several sori are produced near the 
centre of the pinnae, covered by indusia opening 
inwardly with a jagged or irregularly-sinuated mar- 
gin. The plant is evergreen and easy of cultivation. 
It is so common that there is no occasion to give any 
special habitats. It extends to about 600 feet above 
the sea-line. 
In its normal conditions A. Ruta-muraria is easily 
recognizable ; the characters afforded by its triangular 
(deltoid) outline, bipinnate or tripinnate division, and 
distinct wedge-shaped pinnules, together with the 
smallness of the fronds, sufficiently distinguishing it 
from the other Aspleniums. There are, however, cer- 
tain of its forms which are not, at first sight, so easily 
separated from A. germanicum, being narrow on the 
fronds or pinnules, and sometimes scarcely more than 
pinnate. These forms are best distinguished by the 
round-toothed (crenulate) indusia, and by the fine 
even toothing of the anterior margin, — the indusium 
in A. germanicum being entire, and the apex of its 
pinnules being less deeply and unequally notched. 
VARIETIES. 
unilaterale, — Troutbeck, Miss Wright ; Kendal Fell, J. M. 
Barnes. 
cuneatum. — Sizergh, J. Crossfield. 
