.98 Studies in Forestry [CHAP. v. 



marl, iron, or humus, sandy soils are said to be loamy, marly, 

 ferrugineous, or humose. Sands become easily heated or 

 cooled, and have a poor capacity for retaining moisture and 

 nutrient salts in solution ; hence they form the inferior quali- 

 ties of soil, on which trees require a considerable growing-space 

 in order to obtain the requisite supply of food, fail to maintain 

 good leaf-canopy, become deficient in increment,, produce little 

 seed, and are otherwise deficient in reproductive capacity. 

 Owing to their becoming easily warmed by day, they stimulate 

 to the early germination of seed, and movement of sap, and flush- 

 ing of foliage in spring ; but, as they cool rapidly at night, this 

 exposes the young vegetation to danger from late frosts. Earthy 

 ingredients, and humus in particular, improve the quality of 

 sandy soils. When forests approaching maturity show good 

 development on such soils, their natural regeneration is safe 

 and simple ; but where the tree-growth is indifferent, it is advis- 

 able to resort to planting, as the young growth of seedlings is 

 often too intolerant of shade to make natural regeneration under 

 parent standards a success. In the planting up of such soils for 

 the first time, Scots Pine is the best crop, mixed with whatever 

 other species of trees may seem likely to thrive at all well, 

 as, for example, Douglas Fir, Black Pines, Spruce, Menzies 

 Spruce, &c. 



Clayey soils stick if brought in contact with the tongue, and 

 smell of ammonia if breathed upon ; rubbed between thumb 

 and forefinger they feel fatty to the touch, and take a polish 

 or burnish if rubbed with the thumb-nail. They may be grey, 

 yellow, or brownish-red in colour, and are usually tinged 

 with iron. Their leading characteristics are tenacity, weak 

 hygroscopic power, and impermeability to moisture ; but they 

 are strongly retentive of moisture when once saturated. Such 

 soils are cold, and are apt to become water-logged. Any con- 

 siderable admixture of sand, iron, lime, or marl forming sandy, 

 ferrugineous, limy or marly clays tends to modify these char- 

 acteristics. As the soluble nutrient salts are not apt to be 



