504 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
place when the disease is just appearing; (2) careful handling of fruits; and 
(3) the temperature of store room to be kept about 3i°-34° F. The leaf -spot stage 
is controlled by spraying with Burgundy mixture or lime-sulphur wash. Trees 
growing in grass appear to be more susceptible to the leaf-spot form of the 
disease than when the trees are grown in cultivated ground ; consequently it is 
recommended that the soil should be well worked. The control of the canker 
stage falls into three classes, viz. : (1) Surgical methods (pruning, removal of 
diseased bark); (2) Wound treatment (disinfection and protection); and (3) 
Wound healing. Orchard management and resistant varieties are other headings 
under which a deal of information has been amassed, while an excellent biblio- 
graphy completes a useful pamphlet illustrated by photographs and drawings. 
/. K. R. 
Potato Biaek-rot, Caused by Fusarium radicicoia. By O. A. Pratt (Jour. 
Agr. Res. vol. vi. No. 9, May 1916, pp. 297-309; 4 plates).' — This disease is con- 
fined chiefly to potatos of the round type, such as ' Idaho Rural ' and ' Pearl ' ; 
it causes a jelly-like rot as well as a black-rot in potato tubers in Southern Idaho, 
and the organism appears to be well distributed throughout the desert soils 
of this region. The author finds that the disease is checked at a temperature 
of 5o°F., and suggests keeping storage pits at this temperature as a control. 
The disease may also be controlled by planting potatos only on lands which 
have been under other crops for a number of years, and by good tillage. — A. B. 
Potato Dry-rot Disease caused by Fusarium trichothecioides. By O. A. 
Pratt (Jour. Agr. Res. vol. vi. No. 21, Aug. 1916, pp. 817-831 ; 1 plate). — This 
disease is apparently restricted to the arid and semi-arid regions of the Western 
States of America, and may be described as a powdery dry-rot, which is external, 
and arises from bruises in the skin of the tubers. In advanced stages a pinkish 
white growth of the mycelium of the fungus may be observed, and the decayed 
tissue presents shades of colour from black to light brown. The causal organism 
was first described by Jamieson and Wollenwebber in 191 2, and named Fusarium 
trichothecioides Wollenw. Under ordinary field conditions the fungus does 
not attack any part of the growing potato plant ; only potato tubers in storage 
are attacked through bruises. The organism appears to be widely distributed 
throughout Western desert soils. 
Since the fungus does not develop at temperatures below 2°C, a control 
measure is suggested of keeping the storage pits below 2°C. Treatment with 
formaldehyde or mercuric chloride is useful in checking the disease, provided 
the disinfecting is done within twenty-four hours after digging. — A. B. 
Potato Fusaria. By C. D. Sherbakoff (U.S.A. Exp. Stn., Cornell, Mem. 
No. 6, May 1915, pp. 85-270 ; 50 figs., 7 plates). — The purpose of this memoir 
was to lay down a basis for the study of the disease known as fusarial wilt 
and dry rot of potatos. 
The author has collected from all possible sources many different varieties 
of the Fusarium fungus, and has cultivated them in pure cultures on suitable 
media and under similar conditions of growth since the autumn of 1911. 
Over 80 species and varieties of Fusarium are described and figured, as well 
as the related genus Ramularia. Some beautiful three-colour plates of living 
cultures, 40 days old, and grown at a temperature ranging from 20°C. to 25°C. 
are shown. These include sixty of the chief forms of Fusarium. The whole 
memoir is worthy of the great institution in New York State, and represents the 
highest point of scientific literature in plant pathology. — A. B. 
Potato, Late Blight of the (Phytophlhora infeslans). By I. E. Melhus 
(U.S.A. Exp. Stn., Wisconsin, Res. Bull. 37, Aug. 1915. PP- 1-64 ; 8 figs.). — 
The germination and infection with the fungus (Phytophthora infestans) are 
largely dependent upon environmental conditions. How and to what extent 
they react on the spread of the disease is not yet well understood, and the present 
paper is a contribution towards the solution of these important problems. 
The summary of the author's results is as follows : — The spores of this fungus 
may germinate either indirectly by the production of zoospores, or directly by 
germ tubes. The type of germination is determined chiefly by external conditions, 
such as temperature, moisture, and the medium in which the spores are placed. 
Temperatures below 2o°C. have been found to be more favourable for indirect 
or zoospore germination in water than higher temperatures. The minimum 
lies between 2 0 and 3°C, the optimum between I2°and I3°C, and the maximum 
between 24 0 and 25°C. 
For direct or germ tube germination the limits are higher. Direct germina- 
