THE RUE-LEAVEI) KPLEENWORT. 
Asplen ium ruta-muraria. 
Plate 6 , Figs. 9 and 10 , Page 235 . 
A veky diminutive little Fern is Ruta-muraria, so small 
sometimes, even when growing, as it so often does, in the 
most frequented places, as to escape the attention of those 
who are not observant lovers of Nature. Yet, nevertheless, 
it is an extremely interesting little plant. Its specific 
botanical name means simply Wall Rue, and refers to the 
likeness which it bears to the common Rue, and to its habit 
of growing upon old walls. In reality, it is a Rock Fern, 
like all the Spleenworts, but it has a singular fondness for 
old ruins and old walls, a fondness which is due to its liking 
for old mortar. Hence it may often be found growing not 
only upon house and garden walls, but upon church-walls, 
upon bridge-arches, and, indeed, upon all kinds of masonry ; 
being found, however, most abundant and most luxuriant upon 
old stony structures. This partiality forold walls and old ruins 
arises from a cause which will be easily understood. Decay 
in any stony structure is always accompanied by a loosening 
of the parts. Into the fissures created by this loosening 
process, particles of vegetable mould accumulate, brought 
thither either by the decay of leaves which may have fallen 
directly into them, or by the movement of the atmosphere, 
which carries with it light and small particles of vegetable 
and other matter, and deposits them, amongst other places, 
