108 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
which will succeed best in any particular soil, yet a careful 
examination of the latter is indispensable when making a judicious 
choice of plants. The natural vegetation is usually a pretty good in- 
dication of the character of the surface soil, but is not always a safe 
criterion by which to judge the subsoil. Thomson’s ‘ Gardener’s 
Assistant” (p. 38) gives the following list of plants that have 
been observed to grow naturally on different descriptions of 
soils :—** Argillaceous—Tussilago Farfara, Potentilla anserina, 
P. argentea, Orobus tuberosus, Lotus major. Caleareous— Veronica 
spicata, Campanula glomerata, Onobrychis sativa, Lithospermum 
officinale, Nepeta major, [Clematis vitalba]. Silicious—Silene 
anglica, Arenaria rubra, Veronica verna.  Peaty—Vaccinium 
Myrtillus, V. uliginosum, Oxycoceus palustris, Calluna vulgaris, 
Erica cinerea, E. Tetralix, Spergula subulata, Tormentilla erecta, 
Empetrum nigrum, Eriophorum vaginatum, E. polystachyon, and E. 
angustifolium, Sphagnum obtusifolium and S. acutifolium; Rumex 
acetosella indicates a peaty irony soil. Very dry soil—Galium 
verum and G. saxatile, Aira praecox, A. caryophyllea, A. cristata, 
Hieracium pilosella, Arenaria rubra, Thymus serpyllum, Trifolium 
arvense. Wet infertile soil—Juncus squarrosus, J, acutiflorus, 
Cnicus palustris, | Pinguicula vulgaris, Triglochin palustre], various 
species of Carex, Hippuris vulgaris, Epilobium tetragonum, Lyth- 
rum salicaria, Ranunculus lingua, R. flammula, R. acris, R. 
bulbosus, Rumex acetosa, R. crispus. Wet, but not necessarily 
infertile—Poa aquatica, Alopecurus geniculatus, Veronica Becca- 
bunga, Juncus conglomeratus, | Aira caespitosa, Cardamine pra- 
tensis|. Fertility—Cnicus lanceolatus, Urtica dioica, Stellarva 
media, Dactylis glomerata, Poa trivialis. Cold subsoil—Of this, 
Equisetum arvense is peculiarly indicative.” 
When it is intended to plant shallow-rooting coniferous trees 
only, such as Scots fir, larch, and spruce, the character of the 
subsoil is of less consequence, as their roots rarely penetrate to a 
greater depth than 18 inches or 2 feet ; but hardwoods, especially 
oak and ash, send their roots deep into the ground, and the 
subsoil has a greater influence on their growth than on the growth 
of the former. In many cases the surface soil is formed by the 
disintegration of the rock upon which it lies, and therefore the 
character of the subsoil can be easily seen; but in alluvial and 
diluvial deposits it is often of a totally different character, gravel 
and clay frequently lying in juxtaposition. All such formations, 
therefore, should be examined by digging holes here and there 
