Effect of Soil Conditions 59 
the foliage have been changed: an excess of water will cause 
an excess of cambial activity, and this may cause the bark, 
especially on young twigs, to burst open in spots, from a 
few inches to a foot, exposing the wood. This is found 
very frequently on currant bushes, but occurs also in oak, 
horse-chestnut, and beech. ‘To correct this and some other 
similar conditions, the expert surgeon applies a blood-letting 
process, making a longitudinal cut through the bark, whereby 
the pressure is relieved; such a wound soon heals. In other 
trees, like the silver maple, the excessive growth sloughs 
off the old bark, rapidly exposing the younger bark. This 
may be followed up by sum-scald — the drying and breaking 
open of the bark — with the consequences usual to mechan- 
ical injuries. 
A great number of malformations in young shoots, foliage 
and fruit are also attributable to excess of water-supply at 
the root. 
A very common result of the change in the relation of 
consumption to supply of water, as for example, when a 
tree is severely pruned, or in the case of mere excess of water 
at the root, is the formation of so-called water-sprouts, or 
suckers, — very vigorous thin long shoots, which arise form 
dormant buds out of regular order along the branches and 
bole, particularly near cut branches. These may or may 
not be injurious. They interfere, however, with the sym- 
metrical development of the crown, and they are injurious 
when they rob the main branches of water and cause their 
drying out. They should therefore be removed, and at 
the same time the water-supply at the roots regulated. 
Thus, while excess of water on compact soil becomes 
injurious through the impeded aeration of the root system, 
deficiency of water in a drouthy season produces similar 
results by the failure to supply the stream of transpiration 
