652 
phytopathology is therefore a timely and serv- 
iceable contribution. The subject is treated by 
Professor Whetzel in an attractive and per- 
spicuous manner, and covers from the most 
ancient times to the present. Both the devel- 
opment of concepts regarding the nature and 
treatment of diseases as well as the dominat- 
ing influence of phytopathological writers are 
taken into consideration in dividing the time 
into eras, and again into periods. 
Scarcely thirty pages are given to the three 
incubation eras, called the Ancient, Dark and 
Premodern Eras, but they are most readable 
pages, and clearly point out the course of the 
early development of the subject. 
The Modern Era, extending from 1853 to 
1906, was one of great activity in all scientific 
lines. During this time phytopathology be- 
came a distinctive science. Many investiga- 
tors of forceful personality and marked abil- 
ity gave direction to the work of discovery, and 
in consequence the boundary of knowledge in 
the field of plant diseases was enormously ex- 
tended. The center of pathological activity in 
its academic aspects was at first in Germany, 
and in its practical and commercial aspects in 
France, but in both aspects the foremost ad- 
vance began to shift to America in the eighties, 
and soon this country became the leader in 
initiative as well as in the amount of investi- 
gation. 
The present era, now just entering its sec- 
ond decade, has seen the establishment of 
chairs of phytopathology in many universities, 
the rise of the American Phytopathological 
Society and of the journal Phytopathology, 
the enactment of effective quarantine measures 
against the international and interstate move- 
ment of diseased plants, a new class of fungi- 
cides with sulphur in place of copper, the dis- 
covery of the canceroid nature of crown gall, 
and in general the recognition by men of af- 
fairs as well as by the cultivator of the vast 
importance of the utmost detailed information 
regarding plant diseases and of cooperative and 
efficient means for making such knowledge 
available in protecting all sorts of crops and 
plant life. 
This orderly presentation of the evolution of 
SCIENCE 
[N. 8. Vou. XLVIIT, No. 1252 
a science destined to play an increasingly 
wider and more important part in the affairs of 
human well-being and achievement is partic- 
ularly timely. Professor Whetzel has com- 
pressed into the hundred and thirty pages of 
his book a well balanced and helpful outline of 
the historical aspects of the science. It is a 
valuable addition to botanical literature. 
J. C. ARTHUR 
PuRDUE UNIVERSITY 
SPECIAL ARTICLES 
RESISTANCE IN THE AMERICAN CHESTNUT TO 
THE BARK DISEASE 
DurinG the past summer, in connection with 
the Office of Forest Pathology, U. 8S. Depart- 
ment of Agriculture, the writer investigated 
conditions in the American chestnut looking 
toward immunity or disease resistance to the 
well-known bark disease. A thorough search 
was carried on, which, for obvious reasons, was 
restricted mainly to the immediate neighbor- 
hood of New York. City. The results are 
deemed of sufficient importance to warrant 
publication here in advance of a more detailed 
account. 
No immune trees were found, but a con- 
siderable number of resistant trees were lo- 
cated, some of them on the island of Man- 
hattan itself. The following points are con- 
sidered evidence of a resistant quality in these 
trees. 
1. The result of inoculation tests. The 
average lateral growth of the fungus in 289 
inoculations was 0.6 cm. for a period of from 
5 to 6 weeks—mainly in August. This is 
about one fourth the figure (2.2 em.) given by 
Anderson and Rankin for normal trees during 
the month of August at Napanoch, New York, 
and about one fifth the figure (2.83 em.) given 
for the same month by the same investigators 
at Charter Oak, Pennsylvania. 
2. The occurrence of the trees in a neigh- 
borhood long subject to the disease, and the 
presence among the trees of individuals long 
since dead. ; 
1 Anderson, P. J., and Rankin, W. H., ‘‘Endothia 
Canker of Chestnut,’’ Cornell Univ. Agric. Expt. 
Sta. Bull. 347, pp. 574, 575, 1914, 
