194 
political. position it rightfully should occupy. 
That public eulogists of scientific achievement - 
have rarely undertaken to dwell upon any- 
thing beyond the “ practical” result argues 
that there is in them either a want of vision, or 
a lack of courage to force the consideration of 
a viewpoint devoid of popular appeal; perhaps 
both. W. L. Crozier 
Dyer ISLAND 
LEAF BURN OF THE POTATO AND ITS 
RELATION TO THE POTATO LEAF- 
: HOPPER 
THRoucHOUT the northern section of the 
United States, from Montana to New York 
and south at least to Iowa and Ohio, there 
has been a remarkable epidemic of leaf burn 
on potatoes. The margins of the leaves of 
early varieties turned brown, the dead areas 
gradually widening until the leaves dried up 
and the whole field took on a burned ap- 
pearance. In severe cases the stalks also 
withered and died. 
Every potato section of Wisconsin was 
affected and a careful study by the writer 
showed that in every case the injury was 
directly proportioned to the number of potato 
leafhoppers (Hmpoasca malt LeB.) present. 
The nymphs of this species feed on the under- 
sides of the leaves and first produce a wrink- 
ling of the whole surface, with a slight up- 
ward rolling of the margin, and then the 
marginal burning appears. Long after the 
leafhoppers have acquired wings and flown 
away it is possible to determine the cause of 
the damage by observing the cast skins ad- 
hering to the under surfaces and the egg scars 
in the mid rib or veins of the burned leaves. 
In cage experiments, using large numbers of 
leafhoppers, typical leaf burn was produced in 
four days. The relation of this injury to 
what has been previously diagnosed as “tip 
burn” is an interesting subject for future 
determination. The characteristic marginal 
burn is frequently so definite that it is possible 
that there may be something injected that 
produces more definite and widespread results 
than the mere mechanical extraction of the 
sap. There does not, however, seem to be the 
same specific relation that exists between the 
SCIENCE 
[N. S. Vou, XLVIII. No, 1234 
beet-leafhopper and the curly-leaf disease of 
beets. E. D. Batu 
Srate ENTOMOLOGIST, 
Manvison, WIs. 
“FATS AND FATTY DEGENERATION”: A RE- 
SPONSE TO BOOK REVIEWS BY BANCROFT 
AND CLOWES 
Wiper D. Banorort! has recently reviewed 
in the pages of the Journal of Industrial and 
Engineering Chemistry a book entitled “ Fats 
and Fatty Degeneration,’”? by Marian O. 
Hooker and myself. He has also published in 
his Journal of Physical Chemistry a review by 
G. H. A. Clowes,? which in spirit is identical 
with his own. My attempt to answer both of 
these reviews in the pages of Bancroft’s Jour- 
nal has met with the editor’s refusal. 
Bancroft and Clowes’s adverse criticisms are 
of two kinds: (1) those contradicting my ob- 
servations and their interpretation, and (2) 
those implying unacknowledged borrowings 
from the works of others, more specifically 
their own writings. As to the first, it is the 
privilege of any critic to correct errors and to 
disprove arguments when truth and logic are 
on his side; as to the second, no reputable in- 
vestigator would, even if moved by nothing 
better than the low ideal of his material fu- 
ture, jeopardize truth by taking it ready-made 
from another without noting that fact, or 
would pose as the discoverer of laws already 
set forth by authorities working in the same 
field. Those who know either me or the his- 
tory of emulsion chemistry will easily find 
their way here. Yet, deferring to another ar- 
ticle my answer to the scientific objections of 
Bancroft and Clowes—an answer that should 
be apparent to any careful reader of my book 
—I purpose in this note to comment upon 
their purely personal criticism. 
Bancroft says: 
It is also interesting to note that the author does 
not cite Pickering’s first paper, though he must be 
familiar with it. ... It is certainly being over- 
charitable to say that the author has the unhappy 
1 Wilder D. Bancroft, Jour. Ind. and Eng. Chem., 
9, 1156, 1917. 
2Martin H. Fischer and Marian O. Hooker, 
‘«Pats and Fatty Degeneration,’’ New York, 1917. 
3G. H. A. Clowes, Amer. Jour. Phys. Chem., 23, 
73, 1918. 
