SUMMARY, 
215 
7. By Cuttings ; as in sugar-cane. 
This plan is of special value, because the qualities of the parent plant will be main- 
tained by the new one. 
8. By Layers. In layering we only partly separate the cutting until it 
has rooted. 
9. By Budding. \ Buds or cuttings are set in the stem of an old plant 
10. By Grafting, f or tree instead of in the ground. 
These young growths will come into bearing earlier than if they had to start life 
as independent plants. 
HOW SOILS ARE FORMED (p. 80). 
Origin. — Soils are formed naturally by — 
1. The rocks breaking up and crumbling; or by 
2. The remains of plants and animals. 
Forces at Work. — The forces which act upon the rocks are— 
1. Water: 
It softens or dissolves portions of the rock. 
It carries into the rocks the gases the rain gathers from the atmosphere. 
It distributes and mixes the crumbled soil. 
The waves and the running streams wear down the rocks and soil. 
2 . The Atmosphere: 
(1) By chemical changes due to the gases. 
(2) By the force of the winds. 
3. Changes of Temperature : 
(1) Intense heat with drought causes the land to crack. 
(2) Intense cold causes water to freeze, whereby rocks are split and soil 
crumbled ; also, rocks are ground down by moving masses of ice (glaciers). 
4. Vegetation: 
(1) The roots give out an acid which dissolves portions of the soil, and 
thus loosens other portions. They also grow into crevices, and wedge 
pieces of rock or soil away. 
(2) Plants add to the soil by their decay. 
KINDS OF SOIL (p. 83). 
Soils are composed of — 
Sand ; which consists of little grains of a glassy substance, called quartz 
or silica. 
Clay; which consists of silica and alumina. When dry it can be crushed 
into fine powder, and when wet it clings together in a stiff and sticky mass. 
Lime. This is generally found combined with carbonic acid, and is then 
called carbonate of lime ; chalk, limestone, marble, shells, and coral, are all 
various forms of this substance. 
