LUTHER BURBANK 
of bark and wood (called gummosis), to which the 
cherry is peculiarly liable. 
Hybridizing with wild species, intelligently and 
systematically carried out, might produce vari- 
eties of cherry that would show exceptional re- 
sistance to insect pests as well as inherent vitality 
that makes for healthiness in the tree. 
It has long been my belief that a solution of 
the problem of protecting our fruit trees from 
both insect and fungus pests must eventually be 
found in the development of the qualities that 
make for immunity of the trees themselves, 
rather than in the resort to such expedients as 
spraying and “gasing.” In this regard the plant 
experimenter may well take a leaf from the note- 
book of the physician, who has learned that im- 
munity to disease often depends more upon the 
condition of the patient than upon the presence 
or absence of disease germs. 
It is possible, furthermore, that the cherry may 
be hybridized even more widely, and that a fruit 
differing markedly from any cherry hitherto pro- 
duced may thus be developed. An inkling of the 
possibilities in this direction is given by some ex- 
periments made recently by Professor N. E. Han- 
sen, of the South Dakota Experiment Station, who 
has cultivated a variety of wild fruit, called the 
Sand Cherry, Prunus Besseyi, which is a dwarfed, 
[100] 
