ry wide fertilization subsequently with other species. It occurs to
me now--I had no explanation last year, but it occurs to me now,
knowing of Loeb's experiments--that it is possible that one of the
parents, the parent California oak tree carrying the female flowers,
might have had its sex cells subjected to some peculiar influence like
acid, sulphurous acid, for instance, from some nearby chimney.
Sulphurous acid perhaps from someone merely lighting a match to light a
cigar under the tree; he might have so sensitized a few female flowers,
may have so injured the cell membrane of a few female germ cells that
cross pollinization then took place from a walnut tree. It is only on
some such ground as the findings of Loeb that we can explain such a very
unusual hybridization as that, which appeared to me a valid one, of a
cross between an oak and a walnut.

(Secretary Deming then called attention to hybrids in the various
exhibits.)

Professor Smith: I should like to ask why, if this free hybridization
takes place in nature among the hickories, you do not have a perfect
complex of trees showing all possible variations in the forest.

The Chairman: In answer to Professor Smith's question I will start from
his premises and remark that we do have such complexities. The hickories
are so crossed at the present time, like our apples, that even crossing
the pollen of various hickory trees of any one species does not promise
interesting results unless we cross an enormous number. They are already
so widely crossed that it is very difficult sometimes to determine if a
certain tree is shagbark or pignut or shellbark or mockernut. For the
most part the various species and varieties of hickories retain their
identity because their own pollen is handiest, and different species do
not all flower at the same time. Their own pollen from the male flowers
is apt to fall at the time when their own female flowers are ripe and
under these circumstances the chances are very much in favor of the tree
pollinizing its female flowers with its own pollen. On the other hand,
there is hardly one chance in many hundred thousand for any crossed nut
to grow, for the reason that most nuts are destroyed by mice, squirrels,
rats and boys. If you have a hickory nut tree growing in a lot, and
which has produced a bushel of hickory nuts year after year, do you know
of one single nut from that tree which has grown? In this plan of
Nature, this plan of enormous