86 
Pilzkrankheiten der Pflanzen 
/ 
BROOKS, F. T. and PRICE, s. R., A disease of Tomatoes (New Phyto- 
logist 1913, 12, 13—21; 13 text-figs.). 
On the diseased portion of a tomato three fungi were observed: 
Macrosporium sp., Cladosporium sp., and Ascochyta citrullina. By in¬ 
oculation experiments it was shown that the last-named fungus was the 
cause of the disease. Later, one of a consignment of tomato fruits grown 
under glass was found to be affected with the same fungus. As material 
was available both from fruit and from stem it was thought desirable 
to grow the fungus from the two sources on artificial media and to per¬ 
form inoculation experiments. The fungus obtained from the fruit was 
placed in the stems and the fungus from the stem was placed in the 
fruits. In this manner it was hoped to establish more completely the 
identity of the fungus from the two sources. The method of growth of 
the fungus on tomato-agar, tomato-gelatine and pure agar is described: 
as regards behaviour on culture media the fungi derived from the fruit 
and stem respectively are identical. Experiments showed that with green 
fruits infection would only result if the fungus, either in the form of 
mycelium from a pure culture on tomato-gelatine, or of spores, was 
inserted into wounded parts. Inoculations of wounded parts of stems of 
tomato plants were also made with the same mycelium. The results of 
the inoculation experiments made it clear that the fungus causing a rot 
of the fruit is identical with that which induces canker of the stem. The 
perithecial stage of the fungus was never seen. 
J. Ramsbottom (London). 
SMITH, R. E., SMITH, C. 0 . and RAMSEY, H. J. Walnut culture in 
California. Walnut blight (California Agr. Exp. Sta. Bull. 231, 
Aug. 1912, 179 pp., 96 fig.). 
This bulletin represents the results of the most extensive investi¬ 
gation ever made by the Department of Plant Pathology in California. 
The study was undertaken under a state appropriation of $ 4000 made 
in 1905. The first two hundred pages of the bulletin are devoted to a 
description of various species and varieties of walnut, relation of climate 
and cultural methods and marketing. Then follows a dicussion of walnut 
diseases, of which the blight, due to Pseudomonas Juglandis Pierce, is 
the most important and destructive. 
This disease is scatfered over California, and is reported from 
Oregon und Texas. It first appeared in 1891, and was possibly impor¬ 
ted from France on nursery stock. It should not be confused with 
M arsonia Juglandis , which, although not occurring on the English walnut 
in California, is frequent in France. 
The blight may occur on all growing parts of the tree, such as 
young nuts and branches, leaf petioles and veins and adjoining parenchyma, 
producing blackish areas or distinct lesions. The blackening is said to be 
due to the oxidation of tannic acid in the tissues. The damage to young 
nuts is by far the most serious part in the infection. Many fall when 
only one-eight to one-half inch in diameter, and from 50 to 80 % of the 
crop may thus be lost. Infection of the nuts occurs most commonly at 
the stigma end, passing in to the kernel, which it blackens and destroys. 
Leaf, twig and lateral infection of the nuts occurs through the stomates. 
Late infections in summer are of little consequence, 
