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. 
Tf 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 verv 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 aérial 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 
