IO 
siderable and causes the “bleeding” of plants, as_ the 
active exudation of sap is called. This occurs sometimes. 
when trees and shrubs are pruned too late in the spring 
after the sap has begun to rise. The active absorption of 
water takes place in the young roots a little way behind 
the root-tip, where the root can be seen to be covered bv 
a mass of delicate hairs which, possessing very thin walls, 
offer great facility for the penetration of the water. It is. 
important, therefore, in transplanting young plants from 
a seed bed or pan to injure as little as possible the delicate 
young roots, as by pulling instead of carefully digging 
up young plants the absorbtive part of the root anchored: 
by its many hairs may be left behind in the seed bed. 
Plants injured in this way will inevitably suffer a set- 
back, as they will not be able to absorb nutriment 
efficiently until they have developed new roots to take 
the place of those which have been injured. 
Let us now consider the nature of the soil in which 
the roots are growing. We have already seen that to be 
suitable for the growth of ordinary plants it must be well 
drained, whether we are dealing with a plot of ground 
or with pot plants. If the earth becomes water-logged 
the roots are deprived of the necessary air and soon die 
away. The physical condition of the soil is therefore as. 
important as ifs chemical composition. In nature, soils 
are not all equally porous. Some therefore require the 
careful attention of the cultivator. Clay soils particularly 
are liable to retain too much water and need to be 
specially treated for successful cultivation. The retentive. 
power of a soil depends largely on the size of the particles 
of which it is built up. Gravel or coarse sand allows the 
water to pass through it more rapidly than fine sand, and 
even the finest sand is eomipeeen of larger particles than 
those of clay. We can easily prove this by stirring up: 
sand and clay in water. The particles of sand soon settle 
down and allow the water to clear while the water in 
which clay has been stirred up remains muddy for a long 
time. If, however, we add a little lime to this cloudy 
liquid we find that it clears rapidly. This is due to the 
“coagulation” of the very fine particles of clay which 
become collected into larger groups, and these being 
heavier than the single particles of clay, fall to the bottom 
of the water and allow it therefore to become clear. It is 
upon this action of lime upon clay that the practice of 
