THE CULTIVATION OF ALPINE PLANTS. 



287 



The forms in which the rockery, usually so called, can be 

 constructed may be divided into three : (1) The barrow-shaped 

 rockery, (2) the facing rockery, and (3) the sunk rockery. The 

 first may be raised anywhere, the other two depend partly upon 

 the configuration of the ground. No wood or tree roots should 

 be used to supplement any of them ; they must be all stone. 

 The kind of stone is seldom a matter of choice ; everyone will 

 use what is most handy. The rougher and more unshapely the 

 blocks the better. The size should vary from forty or fifty 

 pounds to three or four hundredweight. No mortar or cement 

 for fixing them together must ever be employed ; they must be 

 firmly wedged and interlocked and depend upon one another, 

 and not upon the soil between them, to keep them in their places. 

 This rule is of the utmost importance ; if it is neglected a long 

 frost or an excessive rainfall may cause the whole structure to 

 collapse. 



Each successive part of the stone skeleton must be put 

 together before the soil is added. This applies to all rockeries. 



The most convenient size for the barrow-shaped rockery is 

 about four feet high, and six or seven feet through at the base. 

 The length is immaterial. If the long sides face north-east and 

 south-west it will afford perhaps the best variety of aspect ; but 

 the amount of sunshine each plant gets will depend on the arrange- 

 ment of each stone as much as upon the main structure. There 

 cannot be too many projections, and care must be taken to leave 

 no channels between the stones by which the soil can be washed 

 down to the base. Overhanging brows, beneath which plants 

 can be inserted, are very useful ; large surfaces of stone may here 

 and there be left exposed, and irregularity of form is far better 

 than symmetry. A formal arrangement of flat pockets or nests 

 offends the eye without helping the cultivator, as the tastes of 

 alpines as regards slope of surface and moisture at their roots 

 are very various. As for the degree of slope from the base to 

 the summit of the barrow, it will not be uniform. In some 

 places there will be an irregular square yard of level on the top, 

 bounded by large cross keystones, for which the largest stones 

 should be reserved. In other parts the sides will slope evenly 

 to the ridge ; or the upper half may be perpendicular, leaving 

 only wide crevices to suit the taste of certain plants. If the 

 blocks are very irregular in form, and their points of contact as 



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