86 QUINCE CULTURE. 
more or less protected by a coating of natural varnish, sup-- 
posed to be wax or silica. Whatever it may be, it is best 
to observe what soils and fertilizers supply it. Ashes and - 
lime are found to improve the quality of fruit, and it 
may be assumed, also, that they increase the vigor of 
growth, and so aid in resisting the attacks of bacterial 
and fungoid diseases. 
2. ORANGE Rust (Restilia aurantiaca, Peck; Cen- 
tridium Cydonia, El\lis).—This fungus affects the stems 
and fruit of the quince in June and onward. In asingle 
Fig. 56.—STEM AT A BUD AS AFFECTED BY THE RZSTILIA AURANTIACA, 
instance I have seen it on the leaf stalk. The spores 
are of a beautiful orange color, globose in shape, with a 
membranous envelope, and are produced in sacks or 
pustules, which form an enlargement on the stems, re- 
sembling the black knot of plum and cherry trees. The 
little blackened quinces remaining on the trees after 
the leaves have fallen, attest its destruction of the fruit, 
and warn us against its neglect. Once in a while a stem 
survives its attacks, and so of the fruit. As the disease 
progresses the granules burst, forcing their sides upward, 
