122 MANUAL OF FRUIT DISEASES 



spiration. The abnormally high sap-pressure, of course, comes 

 only when there is a continuous flow of sap, and is usually accom- 

 panied by 'lessened transpiration. Observations strongly indi- 

 cate that the more prominent factors inducing water-core are as 

 follows : - (1) Vigor in trees. Excessive growth, especially in 

 young trees just coming into bearing, is favorable. Such trees 

 do not ordinarily bear a heavy crop, but set only a few, abnor- 

 mally large apples. It has also been noticed that fruits borne 

 near the tips of branches in trees of any age are susceptible to 

 water-core, provided such trees are growing rapidly. On the 

 other hand, trees making a poor growth rarely show glassy fruits. 

 If vigor or unusual vegetative growth be a factor concerned in 

 water-core, then such factors as promote this condition are, in 

 turn, contributing causal factors. High cultivation should be 

 mentioned in this connection. While excessive cultivation alone 

 cannot be held responsible for this disease, it is nevertheless 

 an important factor. (2) Excessive water-supply. Rain or 

 water of irrigation under certain conditions is highly important. 

 If a superabundance of water comes just before maturity of the 

 fruit, and if this excess be accompanied by extremes of tempera- 

 ture and atmospheric humidity, the disease is very likely to 

 appear. Suppose, for example, following a heavy rain-fall the 

 sun warms the soil to such an extent that considerable water is 

 taken up rapidly by the roots. As long as the sun shines the 

 water will be given off by transpiration ; but at night the tem- 

 perature of the air is lowered markedly while that of the soil is 

 not appreciably changed. Thus the roots continue to send 

 water rapidly to the aerial parts, but under the cool atmospheric 

 conditions transpiration is decidedly checked. As a result, the 

 water accumulates in the fruits and there is developed an abnor- 

 mally high pressure. Finally the water is forced into the inter- 

 cellular spaces. Other organs do not show signs of this disease ; 

 the fruits suffer on account of their inability to offer resistance 

 to this abnormal pressure. Those fruits which occupy terminal 



