r<8 
ROCKS AND ROCK-PLANTS. 
by such an appendage ; and in numerous instances where it is necessary, or at all 
events, extremely useful and convenient to have cisterns or small reservoirs in 
various parts of the grounds, they may be rendered very interesting by surrounding 
them with an irregular sloping bank of rock, adorned with showy trailing species 
of plants. 
. We have before alluded to the propriety of selecting smaller pieces of stone, 
and it is quite as desirable to make choice of various sizes. Such also as present 
a rough uneven surface, and differ most widely from each other in general outline, 
are to be preferred before those with a , plain surface. The chinks and crannies 
between them, and every favourable recess which they afford, should be partially 
filled with soil for the plants to take root in, adapted to the predilections of the 
species intended to occupy the several stations. In this manner fragments of rock 
may be piled up to a considerable height against steep banks, or employed to hide 
a wall, with propriety ; and the special adaptability of such a spot for the display 
of trailing plants is by no means of trifling moment. Steep banks of this kind, or 
formed entirely of rough stones run together, will frequently be beneficial, if 
thrown up, with a view to shut out some unseemly object, or to check a current 
of wind in some exposed locality. 
But beyond the benefit conferred of supplying a place when the elegance of 
prostrate species is more apparent, it is also the means of imparting a more mature 
and flowery state with greater certainty than can be gained in some delicate plants 
by other means. Many species, which are constitutionally too tender for the 
ordinary climate of this country, are induced to grow here with singular prosperity, 
even although in the common flower-beds they will scarcely retain life. It will 
be naturally asked, how is this ? In a great measure it is evidently to be ascribed 
to the greater uniformity of moisture. In a dry season a plant in a bed of common 
earth is liable to suffer from a deficiency of moisture, whilst in a wet season it is 
equally subject to be injured by a contrary excess. But planted on rocks it 
enjoys a happy medium : the superabundance of fluid percolates amongst, and 
drains away between the stones ; and if a time of drought follow, the stones 
prevent that rapid evaporation which inevitably takes place when the soil has no 
such protection. Any one may convince himself of the truth of the latter, and of 
its profit to vegetation, by noticing the herbage round a stone in a pasturage or 
corn-field in a dry summer, like that of 1844. 
A redundancy of moisture in the soil, particularly under a still atmosphere, is 
undoubtedly the main cause to which the sudden loss of many species of annuals 
and delicate-rooted half-hardy perennials, is truly referable. We allude princi- 
pally to such plants as Brachycome, Leptosiphon, Zinnia, Salpiglossis, Phlox 
Drummondi and Ipomopsis picta, amongst annuals and biennials ; and to some of 
the small Lobelias and Nierembergias amongst perennials ; and even the herbaceous 
Calceolarias and the rampant-growing Petunias are not entirely exempt from 
"damping off" under the same influence. In winter it is destructive to a still greater 
