SELF-STERILITY IN DEWBERRIES AND BLACKBERRIES 
BY L. R. DETJEN. 
INTRODUCTION 
The phenomenon of sterility may be caused by any one of a number 
of various factors. It may be caused by external agencies, such as 
excessive beat, cold, moisture, and a host of other such conditions; but, 
more frequently, it can be traced to a deep-seated internal origin. 
Sterility is encountered almost everywhere; it ramifies all branches 
of the plant and animal kingdoms. As an agent in the bands of organic 
evolution, sterility plays a role of prime importance, while to the breeder 
of improved forms it not infrequently becomes a menace and a stumbling 
block to further progress. 
Sterility is a factor which is confined not only to the spheres of 
organic improvement and to evolution in general, but also to that of 
the production of fruit crops. In the latter field it becomes a factor 
of the utmost importance. In the planning of the older fruit planta¬ 
tions the factors of sterility were not recognized, and lienee the innumer¬ 
able financial failures, which, by a little knowledge of the comparative 
fertility of varieties, might well have been averted. Examples of this 
faulty planning of fruit plantations are very numerous, and only a few 
concrete examples will suffice to evince the real significance of the factors 
of sterility. Bartlett pear trees when set in large solid blocks have 
generally proven unprofitable to the grower. Y. R. Gardner in bis 
“Pollination of the Sweet Cherry/’ Oregon Experiment Station Bulletin, 
No. 116, points out the fact that among the more recent plantings of the 
sweet cherries, the fruit growers in Oregon have unconsciously selected 
varieties such as Napoleon, Bing, Lambert, and others, which are not 
only self-sterile, but also intersterile, as recent investigations have proven. 
In such cases even the selection of a list of varieties may not always 
constitute a remedy, and such practice when not carefully done may be 
no better than the planting of a whole block of a single self-sterile 
variety. 
The large vineyards of Rotundifolia grapes in North Carolina give 
evidence of a lack of a sufficient number of pollinizers. These vine¬ 
yards were planted upon the supposition that the different varieties of 
Muscadine grapes were self-fertile; but even so, in many instances pro¬ 
vision was made for the cross-pollination of the different varieties. 
Later investigations regarding the self-sterility of rotundifolia grapes 
(N. C. Bulletin, No. 209) produced evidence that all of the cultivated 
varieties of these grapes are self-sterile, and also inter-sterile, and that 
