358 Foreign Trees and Plants [July, 



our forest trees will seldom strike their roots to a greater depth 

 than the height of their foliage, the roots of alpine plants scarcely 

 an inch in height will he found to penetrate the chinks between the 

 rocks full of rich earth, to the depth of sometimes more than a yard, 

 or forty times the height that they venture into the air. The neglect 

 of this most essential condition for the growth of alpine plants is of 

 itself amply sufficient to account for the failure which has generally 

 accompanied the attempts to introduce these lovely flowers to our 

 rockeries. A good depth of soil is indeed more indispensable to 

 these plants than the juesence of rock and stone. They no doubt 

 prefer to expand their flowers and extend their green shoots over 

 the bare rock ; and where rock- work is artistically managed, this 

 faint attempt at a reconstruction of their native habitat adds greatly 

 to the picturesqueness of the effect. But many of them will flourish 

 equally well in open borders, and even when planted in pots, with 

 a few stones about them to protect the roots from the direct action 

 of the sun, if only the two requisites are attended to, of constant 

 moisture and perfect drainage ; and hence they are invaluable ac- 

 quisitions to the cottage or window gardener. The Saxifrages, the 

 beautiful purple Aabrietia, with respect to which 3Ir. Robinson 

 says, " rock-works, ruins, stony places, sloping banks, and rootwork 

 suit it perfectly ; no plant is so easily established in such places, 

 nor will any other alpine plant clothe them so quickly with the 

 desired vegetation," the various species of Arabis, the alpine 

 Primulas, all make excellent bedding plants. The ease with which 

 a new alpine can be domesticated in our climate is shown by the 

 rapid spread of the lovely early forget-me-not, Myosotis dissitiflorcij 

 brought not many years since from the Alps near the Yogelberg, 

 now to be had from every nurseryman, and the treasure of many a 

 cottage garden, with its exquisite sky-blue flowers, continuing from 

 mid- winter till early summer. 



But it is not alpine flowers only which will repay the small 

 amount of trouble necessary for their introduction. Many plants 

 which are never grown without the protection of a greenhouse, do 

 not require any elevation of temperature for their successful growth, 

 but merely an absence of great changes both of temperature and 

 moisture. This is especially the case with not a few of the most 

 delicate ferns, such as the elegant maidenhair, and the two fragile 

 little filmy-ferns ; and the requisite uniformity of temperature and 

 moisture can be obtained out of doors by the erection of a partially 

 underground grotto or ravine of rocks, through which water is per- 

 petually trickling, the entrance being protected by a screen of 

 foliage from the direct influence of the weather. It is astonishing 

 how equable a climate can be obtained by a simple device of this 

 kind. The drawing given on p. 359 is from such a rock-cave 

 constructed in the grounds of one of our most scientific and success- 



