THE NATIONAL NURSERYMAN. 
28 
order to the series or alliance of orders, that I am contin¬ 
ually astonished to find professional men blind to it, and can 
only account for it by supposing they can see little pertain¬ 
ing to grouping beyond the cases of their herbariums, their 
card catalogues, and the ordinal sequence of their books. 
James MacPherson. 
Trenton, N. J. 
SThlRILITY OF PEAR ORCHARDS. 
The U. S. Department of Agriculture is preparing a 
bulletin on the work of Special Agent M. B. Waite in 
Rochester, Brockport and Geneva, N. Y., last fall on the 
subject of sterility of pear orchards. These conclusions are 
drawn : Many of the common varieties of pears require 
cross-pollination, being partially or wholly incapable of set¬ 
ting fruit when limited to their own pollen. Some varieties 
are capable of self-fertilization. Cro«s-pollination is not 
accomplished by applying pollen from another tree of the 
same grafted variety, but is secured by using pollen from a 
tree of a distinct horticultural variety, i. e., which has grown 
from a distinct seed. Pollen from another tree of the same 
variety is no better than from the same tree. This failure to 
fruit is due to the sterility of the pollen and not to mechan¬ 
ical causes. The impotency of the pollen is not due to any 
deficiency of its own, but to the lack of affinity between the 
pollen and the ovules of the same variety. The pollen of 
two varieties may be absolutely self-sterile and at the same 
time perfectly cross-fertile. The state of nutrition of the 
tree and its general environment affects its ability to set fruit 
either with its own pollen or that of another tree. Bees and 
other insects are the agents for the transportation of pollen. 
Bad weather during flowering time has a decidedly injurious 
influence on fruitage by keeping away insect visitors and 
also by affecting the fecundation of the flowers ; conversely, 
fine weather favors cross-pollination and the setting of fruit. 
Pears produced by self-fertilization are very uniform in shape. 
They differ from crosses not only in size and shape, but also 
in some cases in time of maturity and in flavor. Among the 
crosses the differences were slight or variable, so that their 
variations are not to be ascribed with certainty to differences 
in pollen. Self-fecundated pears are deficient in seeds, usu¬ 
ally only having abortive seeds, while the crosses are well- 
supplied with sound seeds. Even with those varieties which 
are capable of self-fecundation the pollen of another variety 
is prepotent, and unless the entrance of foreign pollen be 
prevented the greater number of fruits will be affected by it, 
as shown by the study of Buffum pears. The normal typi¬ 
cal fruits and in most cases the largest and finest specimens 
either of the self-sterile or self-fertile sorts are crosses. 
Practical conclusions : Plant mixed orchards or at 
least avoid planting solid blocks of one variety. It is 
not desirable to have more than three or four rows of 
one variety together, unless experience has shown it to 
be perfectly self-fertile. Where large blocks of trees of 
one variety which blossomed well have failed to fruit for 
a series of years without any apparent reason, it is ex¬ 
ceedingly probable that the failure is due to lack of cross¬ 
pollination. The remedy is to graft in other varieties 
and supply foreign pollen. Be sure there are sufficient 
bees in the neighborhood or within two or three miles to 
properly visit the blossoms. When feasible endeavor to 
favor insect visits to the blossoms by selecting sheltered 
situations or by planting windbreaks.” 
Referring to the experiments in Rochester, Mr. 
Waite says: “These experiments were carried on in 
the large variety orchard of Ellwanger & Barry, within 
the limits of the city of Rochester. Every facility for 
making them was kindly afforded by the proprietors. 
Without this fine collection, many trees of which were 
planted years ago, and the generosity of the owners in 
placing it at our disposal, the number of results possi¬ 
ble would have been very much smaller. This pear col¬ 
lection, which was the pride of the late Patrick Barry, 
probably contains more varieties than any other in 
America. On a few acres of ground there are here to 
be found about all the pears commonly cultivated in the 
United States and many of the rarer ones. It is scarcely 
necessary to say that the trees have received intelligent 
and excellent cultural treatment, and were, with very 
few exceptions, in fine condition. The orchard was 
reached May 7th, before the flowering began. The 
blossoms commenced to open May 14th ; on May 15th, 
the earlier-blossoming varieties were about one-fourth 
out and the others beginning to open, and on May i6th 
all but a few exceptionally late-blooming sorts were well 
in flower. Paper bags were put on a large number of 
varieties on May 16th-17th, just before the flowering. 
On the latter date it was necessary to remove an occa¬ 
sional opened flower in order to include in the bags cnly 
unopened buds. A greater number of experiments were 
made here than at all the other places together, the 
general result being in accordance with those secured 
before. The Bartlett pollen was found to be almost 
but not absolutely sterile in producing fruits on stigmas 
of its own variety, and very much inferior to other vari¬ 
eties, but was shown to be perfectly good pollen when 
applied to other varieties. Of the forty varieties worked 
on, about two-thirds were nearly or quite sterile to their 
own pollen. It was found that other varieties, such as 
Clairgeaux and Lawrence, were even more completely 
sterile to their own pollen than was the Bartlett. 
There were two especially new features developed 
by the Rochester series aside from other points, (i) that 
the Bartlett and Anjou are not absolutely sterile to their 
own pollen, but under favorable conditions can set a 
few fruits under its influence ; that Angouleme, Seckel 
and other varieties which seem self-fertile were not al¬ 
ways as productive when limited to their own pollen as 
when cross-pollinated.” 
