BUTLER: ALTERNATE BEARING IN THE APPLE 91 
After the flowers have been pollinated and the fruit has set the 
lower and leafy portion of the floral axis becomes considerably 
thickened and pursey (PLATE I, FIG. 1), hence the name bourse given 
to it by the French and which Dr. Black* has very appropriately 
anglicized purse. On this purse one or two axillary buds either 
become spurs, darts or sprigs, or if placed terminally on a leader 
may and usually do develop a shoot. The spurs form during the 
current year and either flower the following spring, or, and 
customarily only do, develop a flower-bud during the second season 
and bloom in the third, but, should the purse eyes remain dormant 
the year of their formation then the spurs would not bloom until 
the fourth year; the darts, which develop readily on purses (see 
PLATE I, FIG. 1) and sprigs flower in the usual way. 
Owing to the fact that with few exceptions, spurs only flower 
on alternate years it must follow that after an apple tree begins to 
form new growth slowly and bear heavily, a light crop must 
necessarily follow a heavy crop, for, when the flowering of the 
spurs synchronizes to such an extent as to give a large yield, the 
same spurs are not in a position to bear again until the next suc- 
ceeding year. Alternate bearing in mature apple trees is, there- 
fore, a natural phenomenon and one that could be predicated 
from the mode of flowering of the tree. 
III 
Alternate bearing of the apple has been ascribed very generally 
to exhaustion following the productive year, but this opinion 
appears to be without foundation, for it is commonly observed 
that an apple grows well following a productive year which would 
not possibly be the case were the tree exhausted. Again if the 
tree were exhausted when it bore heavily it is to be presumed that 
the spurs would require a longer time to produce flowers than 
they do when production is light, for a spur weakened from any 
cause is not a fruitful spur any more than is one that develops with 
too much vigor. Nor is there any particular justification in 
Gourley’s view that there is a relation between the amount of 
starch stored and flower bud development. Flower buds may be 
* Black, C. A. The nature of the inflorescence and fruit of Pyrus Malus. Mem. 
New York Bot. Gard. 6: 521. 1916. 
+ Gourley, J. H. loc. cit. 
