Nov., 1923] 
DORSEY-STERILITY AND HORTICULTURE 
477 
crosses the number of achenes which develop is surprisingly limited. In 
North Carolina, 11 out of 15 varieties of dewberries and 4 out of 16 of the 
blackberries were found to be self-sterile (Detjen, 1916). In mixed plantings 
Ancient Britain sometimes sets lightly. In the brambles a considerable 
number of drupelets can fail to develop before the berries become un¬ 
marketable. Counts made with ripe red raspberries (varieties Cuthbert and 
Latham) showed that as many as ten to fifteen percent of the drupelets 
had failed to develop in apparently perfect berries; when the percentage 
ran higher than this, both size and uniformity were affected. 
In the currant and the gooseberry, self- and cross-sterility results in the 
loss of flowers from the clusters, especially at the tip, and in small fruits 
with few seeds. Imperfect clusters vary with the season and variety, but 
pollination and position appear to be important factors. In the black 
currant the pollen is sticky, and artificial pollinations resulted in nearly 
a perfect set in some varieties (Wellington, Hatton, and Amos, 1921; Hatton 
and Amos, 1921). In these varieties the length of the style proved to be 
an important consideration, because self-pollinations took place when the 
style was long enough to bring the anthers in direct contact with the stigma. 
Of the black currants studied, all varieties were self- and cross-fertile. The 
dropping of flowers, generally from the terminal part of the cluster, is one 
of the most serious difficulties in the currant. 
This phase of the subject might be discussed further, but the above 
summaries will suffice to illustrate the status of fruit-setting in the principal 
fruits. It will be seen that the sterility problem is different in each and 
that it varies in degree of importance. A critical survey of the general 
condition reported above indicates that the factors which condition fruit¬ 
setting may be thrown roughly into three main categories, namely, weather, 
genetics, and nutrition. These will be considered more in detail in the 
order of mention. 
The treatment of these will be clearer if a classification is made at this 
point of the possible fate of flowers. A study of the life history shows three 
distinct periods of dehiscence. These are: (a) the first drop, which in¬ 
cludes all pistils in which growth is stopped before the embryo sac is com¬ 
pletely formed; (b) the second drop, which includes all pistils in which 
fertilization has failed to take place; and (c) the third, or June, drop, which 
is made up of those fruits in which the embryo has aborted. This classifica¬ 
tion does not take into account winter killing or spring frost injury. The 
effect of the loss of pistils at the different drops will vary with the fruiting 
habit. It will be seen, then, that there are certain definite causes to which 
the loss of flowers which do not mature must be attributed. 
The Relation of Weather to the Set of Fruit. Unfavorable weather causes 
more crop failures and irregularities in production than any other single 
cause. Fruit buds may be injured by low temperatures during dormancy 
or after growth has started following the break in the rest period, in late 
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