22 
jNT. C. Agricultural Experiment Station 
detrimental to some species or varieties than to others, and that for this 
reason varieties might behave differently. Allowing due credit for this 
fact, we nevertheless find that under normal conditions, and with 
varieties interplanted for cross-pollination, we get normal crops of 
fruit from all with the exception of Manatee. This fact is sufficient evi¬ 
dence that soil and soil-fertility factors must be separated and elimi¬ 
nated from the real causes that underlie the phenomenon of sterility 
of varieties in dewberries and dewberry hybrids. 
Another factor of environment, namely, that of late spring frosts, must 
here be considered, because in this case the different varieties are not 
similarly affected. Some varieties of dewberries and hybrids are more 
subsceptible to cold than are some others. 
Late spring frosts may destroy a berry crop in two different ways: 
first, by killing outright the succulent growth of vines that begin 
activity of growth during the early warm spells of late winter; and 
second, by the injury of the blooms of early flowering varieties. The crop 
of blooms for the season being destroyed, but very little fruit from such 
varieties can be expected during the following season. 
Although all of the varieties of dewberries that have their origin in 
Rubus trivialis (and also the four hybrid varieties, Haupt, Sorsby, 
Spalding, and McDonald,^which, from evidence derived from Table ISTo. 
1. prove to be self- i o rtiffi belong to this group of early growers, and 
although it frequently happens that in this locality, as well as elsewhere, 
these varieties frequently have their crop of fruit considerably diminished 
by late spring frosts, the fact yet remains that during normal years 
these same varieties bring forth a bountiful supply of fruits. Thus, late 
spring frosts cannot be regarded as the cause of the general sterility of 
dewberries and their hybrid varieties. 
Sterility Due to Hybridism .—That the mating of two widely separated 
species of plants or of animals frequently produces sterility in the off¬ 
spring is a recognized fact. As an example, Dr. Peter Wylie in his report 
on the breeding of grapes wrote as follows: “We can impregnate the 
foreign (Vitis vinifera ) with pollen from the Scruppernong, producing 
thereby only male (staminate) plants and imperfect hermaphrodite or 
pistillate plants, which bear no fruit.” Again, all of Bogers’ hybrids 
which are the offspring of native species of grapes crossed with pollen 
from Vitis vinifera are with only one exception self-sterile. 
Any investigation as to the sterility of any variety of plants would be 
incomplete if it omitted altogether this important factor of ancestry. 
By investigating the botanical characters of our cultivated varieties 
of dewberries we arrive at certain definite conclusions: First, that most 
of our cultivated varieties of dewberries, as near as we can ascertain, 
are direct lineal descendants from native species, and that but few. are 
hybrids. Second, that generally the direct descendants of these native 
species retain the same relationship to the question of fertility exhibited 
by the parental species. An exception to this rule is found in the case 
