Self-sterility in Dewberries and Blackberries 
21 
of its ovules did not receive tlie proper amount of pollen that is re¬ 
quired for complete fertilization. Hence a large number of nubbins are 
produced instead of the well developed berries. The real cause of 
sterility, however, lias not yet been reached. 
Sterility Due to Environmental Conditions .—It is a fact that trees and 
plants which are generally self-fertile, under normal conditions, will 
produce an abundance of fruit, but which when subjected to abnormal 
conditions, such as a superfluity of moisture, an abnormal amount of 
nitrogen in the soil, late spring frosts, etc., will forego the production of 
fruit. In order to forestall any influences that might find their origin 
in the environs of the plants under our observation, the test plants in 
our experimental field were laid out in the following manner : 
A square field, having approximately an area of two and one-half 
acres, was divided into two nearly equal parts, the division line extend¬ 
ing from west to east. The northern half was devoted entirely to black¬ 
berries and blackberry-dewberry hybrids, and the southern half to 
dewberries and dewberry blackberry hybrids. Each half of the field was 
further subdivided into equal sized plats sufficiently large to accommo¬ 
date three rows of each of the varieties with thirty plants to the row. 
The plants and the rows lie in a north and south direction. The distances 
between the plants in the rows, the rows from one another, and the 
spaces between the separate plants were made equal and uniformly at 
five feet. The ivliole field was laid ofi on the square system. Thus, the 
whole collection of test plats has the appearance of a regular fruit 
plantation. Ho especial care was exercised in the selection of varieties 
which were to occupy the successive plats of the plantation; however, 
it so happened, as was later discovered, that the self-fertile and the 
self-sterile varieties were pretty well mingled. 
The square system of planting made possible the uniform cultivation 
of the individual plants in both directions, and made impossible un¬ 
conscious differences in the treatment of the individual plats. 
The soil of this berry plantation is a sandy loam underlaid with a clay 
subsoil and is as nearly uniform as it was possible to secure. Fertilizers 
were applied semiannually to the plantation as a whole, the phosphates 
and potash predominating in the spring application and the nitrogen 
element predominating in the summer application. 
The cultivation of the individual plats consisted in the cultivation of 
the plantation as a whole; clean culture in the spring and summer, and 
a cover crop of rye or of cowpeas in the fall and winter. Thus the soil 
treatment accorded to one plat was accorded to all, and therefore the 
environment of one variety became, as nearly as was possible to make 
it, the environment of each and all other varieties. 
If, then, the environment be the cause of the sterility of the different 
varieties, we should anticipate either sterility in all of the varieties or no 
sterility in any of them. It might he contended, however, that the con¬ 
ditions to which all of these varieties were subjected might he more 
