236
THE ESSEX NATURALIST.
England now with those "races" that appear, from their mor-
phological characters, to be derivates of Emmer.
The economic botanist will appreciate the advantage of Prof.
Percival's decision to restrict the term "species" to the two wild
grasses which belong to the genus, and to employ the term
"race" for those cultivated forms that seem entitled to rank as
entities apart. The only objection the taxonomic botanist can
take to this arrangement is that it involves the use of distinct
names for a wild "species" and a cultivated "race" that differ
less from each other in appearance than spontaneous Woad does
from its cultivated condition. This wild "species," together
with its cultivated form, constitute the first of the three "series"
in which Prof. Percival arranges the wheats. His second "series"
includes the other wild "species" ; all the "varieties" of its culti-
vated condition ; and all the "races" that appear to be derivates
of this cultivated "race." His third "series," which includes
no wild "species," contains the group of "races" of which Bread
Wheat is the most important.
The anatomical and morphological evidence on which Prof.
Percival's arrangement is based owed little to cytological co-
operation. Though Prof. Percival was aware that the number of
chromosomes is not the same for all races of wheat, cytologists
generally, prior to 1918, appear to have been satisfied that in
Wheat the basic haploid number of chromosomes was 8. But in
1918 Dr. Sax reported approximations to 7 as the haploid number
in the most important of the "races" derived from Emmer, and
Mr. Sakamura, working chiefly with root-tips, was convinced that
in the "races" belonging to Prof. Percival's third "series "there
are 42 chromosomes ; in the "races" belonging to the second
"series," 28 chromosomes ; in the solitary "race" which con-
stitutes the first "series," 14 chromosomes. We can understand
why, in 1921, Prof. Percival should have written : "this series
"with 7 instead of 8 as the basic haploid number is remarkable"
and have added "these numbers require further investigation."
We gather from what Mr. Haldane said a year ago, that the
further investigation required has been carried out by Prof.
Vavilov and his assistants ; that the results obtained by Mr.
Sakamura have been confirmed ; and that, what is of immediate
interest to us, the arrangement of the species, races and varieties
proposed by Prof. Percival does not call for substantial modifi-
cation .