168 QUINCE CULTURE, 
excess of phosphoric acid over that of the diseased fruit. 
The healthy fruit also contains a decidedly smaller por- 
tion of potassium. All comparisons of lime, potash and 
phosphoric acid which follow, are based on ash free of 
silica, carbonic acid and unburned carbon. 
The conclusions derived from these data are: that the 
rot prevents the fruit of the quince from absorbing its 
normal portion of phosphoric acid and tends to increase 
the potassium, and indicates that a liberal fertilization 
with phosphoric acid might stimulate the tree in some 
way to withstand the ravages of the rot. 
In respect of the roots of the healthy and diseased 
trees, it is interesting to note that the healthy trees con- 
tain far less silica in the roots than those of the trees 
killed by the borers; the proportion being less than one- 
half. This may be explained by the fact that the soil 
may work its way into the holes made by the borers. 
The roots of the healthy trees also contain very much 
larger quantities of potassium than those of the injured 
trees; while, on the other hand, the proportion of phos- 
phoric acid present in the ash of the healthy roots is 
decidedly less than that in the ash of the injured roots. 
The injured roots also have a larger quantity of lime. 
In regard to the twigs, there is a most striking differ- 
ence between the ash of the healthy twigs and of the 
twigs killed by the fungus. This difference is found in 
the practical exchange of the per cents of potash and 
lime. In the healthy twigs the lime is in large excess 
over the potash, while in the diseased twigs the potash 
is in very’ large excess over the lime. This is a most 
remarkable fact and shows the effect which the disease 
has upon the normal absorbing power of the twigs 
themselves. 
In regard to the ash of the wood from the trees killed 
by borers and blight, it is found that the potash in the 
wood killed by blight is in excess of the same constitu- 
