THE MEDITERRANEAN NATURALIST 
It tells its own tale readily enough, and almost 
seems to be proud of the work of destruction in 
which it has been concerned, and which 'ultimately 
brought about its own ruin. In a fissure of the 
Upper Limestone, a deposit which forms the cap- 
ping of all of the hills in Gozoand Malta, it had, 
in bygone years, taken root; and had disseminated 
a perfect network of tough fibrous tendrils through- 
out every available nook and cranny. 
In the mean time, thesubjacent Sand and Clay beds 
had been slowly eroded away by the atmospheric 
agencies that had been constantly assailing them, 
and thus the Upper Limestone masses, having been 
deprived of their foundations, were left in a state 
of unstable equilibrium, which rendered them 
susceptible of the least mechanical strain, whether 
exerted from above or below. 
The end soon came. Many of the rootlets had 
decayed, and becoming intermixed with other 
vegetable matter that bad entered the fissure with 
the rain, a humus had formed, from which carbonic 
acid gas was evolved; this, acting on the limestone 
caused an enlargement of the fissure, and the mass’ 
of rock thus attacked and weakened in every 
direction, at length broke o ff from the parent bed, 
and thundered down the slopes to the bottom of 
the valley. The tree was reft in twain by the force 
of the separation; and now gaunt and bare, its 
mutilated trunk sway, loand fro with every breeze, 
as though moaning over the fate that had depri- 
ved it of its erstwhile home. 
“Cast anchor in the rifted rock, 
And o'er the giddy chasm filing 
His shattered trunk, and frequent flung, 
Where seemed the cliffs to meet on high, 
His bows athwart the narrowed sky.” 
Among the multiplicity of causes at work, hol- 
lowing and scooping out the oaves that occur so 
plentifully all along the escarped sides of the 
valley, none are more indefatigable in their exer- 
tions to forward the work of destruction than the 
innocent-looking, sweet-smelling mint (Melissa 
officinalis), and the delicately-formed maiden-hair 
ferns, with which the walls am 1 floors of the caverns 
are often draped. Carefully remove two or three 
of these plants from tlieir places, and note how 
they have converted the upper film of the rock 
;tself into a soil wherewith to assist them in their 
3 OS 
struggle for existence. Yonder wall, with it s rich 
green mantle of ivy, deserves, too, a share of atten- 
tion. How the tendrils of this hardy little creeper 
have inserted themselves into the most impossible 
of places, and have threaded and rethreaded the 
interstices until they have bound the whole mass 
as no mortar could have done it; but let us lift 
this grey, green garb and expose the rottenness 
that exists beneath. The stones appear to be in a 
rapid state of decay, owing to the humid nature of 
their surroundings, a state which is clearly attri- 
butable to the plant-life that covers them, for see, 
those very parts that are not so covered, have suc- 
cessfully withstood all the combined attacks of the 
atmospheric forces to which they have been sub- 
jected. 
But of all of the plants that contribute towards 
this wasting away of the island deposits, the cactus 
or prickly-pear stands pre-eminently the first, as 
being the one to which the most mischief is due. 
This plant is extremely hardy, and grows in great 
abundance, anywhere and everywhere in the 
islands. No soil seems to be too poor for it to 
take root in; and as soon as one of its oval, fleshy 
leaves is set, in the course of a comparatively short 
space of time a small forest of them may be antici- 
pated. It often attains a considerable size, ranging 
from one to fifteen feet in height, and the fruit, 
which is of a rich, red and yellow colour, is .used 
by the peasantry as food, both for themselves and 
for their cattle. Like all other trees of vigorous 
growth, it does not confine itself to the soil, but 
causes its roots to ramify in all directions; and 
wherever it is possible it penetrates the underlying 
strata in search of those phosphates and carbonates 
that are necessary to its existence, and in which 
the soil may be deficient. 
But the work of breaking up the rocks and con- 
verting them into soil represents only a very small 
proportion of the actual part which it [flays as an 
agent of degradation. 
The humus, formed by its decaying portions 
evolves large quantities of carbonic acid gas, or 
carbonic dioxide, and this, when dissolved imparts 
to the water some peculiarly destructive properties. 
Pure rain-water, when alone, lias but little effect 
upon lime; but, in conjunction with this gas, its 
dissolving powers are increased fifty-fold. 
The rain-water that descends upon this decaying 
mass of vegetable matter, saturates itself with the 
