404 
FRTJIT BLOSSOMS 
vated in this country,” says Waugh, “their 
general self-sterility was a drawback, 
which in many cases proved fatal to their 
success.” Waugh’s observations extended 
over five years and included many varieties, 
especially of native species. All the varie¬ 
ties of American plums proved self-sterile, 
with the exception of the Robinson, and this 
variety is not wholly reliable when self- 
pollinated. The Japanese plums were also 
found to be generally self-sterile. Of the 
European plums a part seem to be self- 
sterile and a part self-fertile, but no satis¬ 
factory experiments are on record. All of 
the hybrids are self-sterile. The experi¬ 
ments made, says Waugh, show beyond 
question that the majority of plums do not 
bear well, and most of them set no fruit at 
all unless two or three varieties are mixed 
in the same orchard. The reason for this 
is that the blossoms of most varieties do 
not pollinate themselves. In general the 
varieties in each group pollinate each other 
better than they do varieties belonging to 
another group. (Waugh, F. A., “Plums and 
Plum Culture;” also Bulletins 53, 67, 89, 
etc., Vermont Experiment Station.) 
Self-sterility in plums may be due to 
several causes. The stigmas may mature 
two, three, or even five days before the 
anthers. A part of the pistils may be de¬ 
fective, but usually there are enough per¬ 
fect pistils to ensure a full crop. The pol¬ 
len may be impotent. The stamens are 
shorter or at least do not exceed the pistils 
in length so that pollen cannot fall on the 
Stigmas unless the flowers stand sidewise. 
The plums bloom profusely, and the limbs 
of the Japanese varieties are often com¬ 
pletely wreathed with flowers. In small or¬ 
chards the air is filled with insects hover¬ 
ing about the trees. In a little over an 
hour the writer collected 100 specimens of 
wild bees, mostly species of Andrena and 
Halictus, and these were only a small part 
of the number present. Honeybees are also 
frequent visitors, both sucking nectar and 
collecting pollen. Wild bees man cannot 
control, but he can raise honeybees, and 
horticulturists recommend that he place 
them in large numbers in the orchards. 
THE POLLINATION OP THE PRUNE. 
Prunes are varieties of plums containing 
so little moisture that they can be dried in 
the sun or in evaporators. Large quanti¬ 
ties of prunes are produced in France, 
Spain, Germany, and Serbia. In America 
prunes are raised chiefly in California, 
and, to a less extent, in Oregon. The Santa 
Clara Valley in California is largely plant¬ 
ed with prunes, principally the French va¬ 
riety, with smaller interplantings here and 
there of the Sugar and Imperial varieties. 
No other dried fruit is sold in that State 
in such large quantities. During the height 
of the blooming season in the Santa Clara 
Valley a great scarcity of insects, especial¬ 
ly bees, has been observed. In some locali¬ 
ties one might work for days among the 
blossoms without seeing a bee. 
To test the value of honeybees as polli¬ 
nators of prune trees a series of experi¬ 
ments has been made by the Berkeley 
Agricultural Experiment Station in an or¬ 
chard of 180 acres on the Sorosis Ranch in 
Santa Clara County. The orchard con¬ 
tains chiefly French (Agen) prunes, 18 to 
25 years old; but there are four rows of 
Imperial prunes. In the entire orchard in 
1916 there were only six colonies of bees, 
and only 3.6 per cent of the blossoms of 
the French variety set fruit; but in 1917, 
with 115 colonies 13.2 per cent of the 
flowers set fruit. The Imperial variety 
yielded equally well (7.2 per cent) during 
both years, and showed no response to the 
increased number of hives. Other orchard- 
ists obtained equally favorable results. At 
Saratoga 50 hives of bees were placed near 
the edge of a 50-acre prune orchard, and 
the branches were literally broken down 
under the burden of the crop. A cherry 
orchard near by also yielded a large crop. 
In another orchard in Santa' Clara there 
were 50 hives, and the trees were loaded to 
their full capacity. At Yuba City 113 
hives were placed in a mixed orchard, and 
all varieties of trees yielded exceptionally 
heavy crops, which were attributed by the 
owner to the agency of bees. Branches of 
trees covered with netting produced no 
fruit. 
At the Sorosis Ranch a tree of the 
French prune was enclosed alone in a tent 
of mosquito netting, and all insects ex¬ 
cluded. Altho covered with blossoms, less 
than one-half of one per cent (0.43) of 
them set fruit. Under similar conditions 
only 0.34 per cent of the blossoms of a 
