1916] HOAR—STERILITY IN RUBUS 375 
are matured. He has shown, moreover, that below the angio- - 
sperms a comparatively small amount of sterility occurs, and that 
in the gymnosperms it is almost entirely absent. On the other 
hand, the angiosperms present a yery different aspect. Certain 
families of the last have long been a puzzle to the systematist. 
BATESON (22) points out that in Oenothera Lamarckiana a large 
percentage of sterile pollen is present. Other geneticists and 
cytologists, including DEVries himself, have noted this, but per- 
haps BaTEson was the first to attribute it to hybridization. Jrr- 
FREY (21) has shown’ that the condition of abortive pollen is 
characteristic not only of Oenothera Lamarckiana, but of the Oeno- 
thera species in general, and that, moreover, the entire family of 
the Onagraceae is so characterized. Because of this he considers 
that DeVries’ ‘“Mutationstheorie,”’ in so far as it is based upon 
Ocenothera Lamarckiana, is lacking in justification. In other words, 
in order to establish such a theory securely, one must deal with 
plants and with animals which are species in the fullest sense of the 
word. Geneticists have long recognized the variability of hybrids, 
and hence plants with any trace of hybridization should not be 
used as a basis for a theory of such fundamental importance as 
that promulgated by DeVries. In a recent article DEVRIES (23) 
has attempted to refute JEFFREY’s contention that pollen sterility 
is a criterion for hybridization. He states that, from such a view- 
point, we might consider the abortion of the 3 mother cells in the 
formation of the mature egg, which customarily takes place in the 
angiosperms, as a criterion for their hybrid origin. Again, he 
cites the case of certain sedges in which ordinarily 3 of the pollen 
mother cells abort and we find their remnants clinging to the 
mature pollen grain. His examples appear to me to be chosen 
from conditions which have no direct relation to the situation 
found by Jerrrey. 
After what I have just said it is fitting, perhaps, to add a few 
words as to what really helps to make up a true species. In attempt- 
ing such a discussion I realize that I am treading upon more or less 
forbidden ground; however, I shall give views which seem to me 
to be well supported by the observations of experts. There are 
those who would separate the idea of species entirely from that of a 
