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, w^herebv 

 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 sun-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 w^ater 

 at the root, is the formation of so-called water-sprouts, or 

 suckers, — very ^'igorous 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 



