ROCKS AND ROCK-PLANTS. 
89 
juniber, even amongst plants that are quite hardy enough to endure several 
legrees of frost ; and to some of our native species, which, when favourably 
j.tuated at the roots, will brave the sternest winters in the most exposed localities; 
(f which the rock-rose {Helianthemum) is a familiar example. And here we may 
emark, en passant^ that in all cases where this family are cultivated in common 
iower-beds, they must not only be well drained at the roots, but the surface 
lould be covered with small pebbles, shells, or pieces of brick, to prevent the 
(loots from resting directly on the damp earth. Of course, on the side of a hill 
diere they are exposed to brisk winds, and more in their natural circumstances, 
iiey are not so liable to harm without the pebbles, as in low or level situations. 
)ecided succulents, such as Sedums, Sempervivums, and the hardier species of 
ilacti in summer, together with the whole race of alpines, are rarely so successfully 
iianaged in the open garden in any other way, as in situations similar to that we 
re now advocating. 
We have occasionally seen very engaging effects created by masses of the 
ommon scarlet 'Pelargonium planted on a pile of rough stones, having the inter- 
' ices filled with mould. Under these circumstances, the excessive luxuriance of the 
lecies is held in check, and a more speedy and copious bloom unfolded. Petunia^ 
Jolana, Salvia^ Ampliicome arguta acquire an earlier and a more floriferous habit, 
'he Mesembryanthemum tricolor (or M. pyropceum^ as it is also called) is a 
elightful object when cultivated thus, in extensive patches ; and the contrast of 
nt which stones afford in a natural state — that is, worn with time, and not 
resenting any recent clefts — is a great enhancement ; through lending a more 
|ecided character to the colours and appearance of the flowers and foliage, without 
■eing, in the smallest sense, destructive of harmony. 
I We might multiply instances almost beyond number of beautiful things that 
'e benefitted by the kind of situation here broached ; but our object is rather to 
raw attention to its influence generally than to individualise farther than is 
scessary to the explanation of the subject, and to indicate the kind of plants 
rhich are capable of a more exalted character, or extensive culture beneath its 
i'orking. 
I We have yet to invite deliberation specifically to its adoption in the narrow 
orders attached to the front of those plant-houses having a low parapet wall, with 
' view to their amelioration and increased adaptability for the reception of stove 
Ad the more tender greenhouse exotics. Few, we imagine, will attempt to 
nnsay the desirableness of extending the cultivation of such plants as the 
chimenes coccinea^ the delicate Thunbergias, Alstroemerias, and similar attractive 
nogs, amongst which we may include a vast number of species belonging to the 
maryllis and Iris tribes ; and these can be made to grow and flower favourably 
•1 similarly protected places to those we have just alluded to. 
' In addition to what has been already advanced as influential in augmenting 
le power of a delicate exotic to exist and flourish in the open air, we must now 
VOL. XII. NO. CXXXVI. N 
