DISEASES OF PLANTS. 749 



tissues of cacao throngli wounds. i)rocluciug a disease, but this was not the 

 common canker or pod rot. 



Spraying has proved the most practical and successful method for combating 

 both pod rot and canker, but further work will have to be done before the best 

 mixtures, times for application, machinery, etc., can be positively known. For 

 the present, it is advocated that the trees be sprayed at least four times a year, 

 the applications being made when the trees are well covered with young fruit, 

 but not when in full bloom. 



A bibliography of cacao diseases is appended. 



A new coffee disease (Phthora vastatrix), F, H. D'Heeelle (An. Soc. Rural 

 Argentina, 44 (1910), No. 68, pp. 40-45, figs. I4). — In a further discussion 

 (E. S. R., 22. p. 151) of this very destructive coffee disease, the characteristics of 

 the fungus, its method of dissemination, and suggestions as to its control are 

 given. 



The first symptom of the disease is the appearance on the trunk near the 

 ground of cracks in the bark, beneath which the exposed wood shows black 

 throughout. This diseased condition extends beneath the bark to a height of 

 3 or 4 ft. above the ground, while the upper part of the trunk and the limbs are 

 fi'ee from the disease. 



The fungus usually invades the roots by spore infection. The death of the 

 tree is caused by the hyphie plugging the conducting tissues and by the destruc- 

 tion of the cambium. 



The total duration of the disease is from 24 to 2G months, and always ter- 

 minates in the death of the tree. The fruiting stroma of the fungus bearing 

 perithecia is found beneath the bark on the blackened wood. The fungus is 

 said to have 4 kinds of spores, viz, ascospores, conidia, pycnospores, and 

 stylospores. 



The disease also attacks 2 species of luga (Cuxil and Paterno) used as shade 

 trees for the coffee. 



The remedies proposed for the disease are heavy liming of the soil, the use 

 of nonacid fertilizers, so pruning the coft'ee i)lants as to obtain a better circula- 

 tion of air and more sunshine on the ground, and the planting of trees for wind- 

 breaks and to catch the spores. In making new plantations it is advised that 

 the rows be run east and west, that the coffee plants be set farther apart, and 

 that, if shade trees are usetl, species of trees be planted which are not suscepti- 

 ble to the di.sease. 



On the infection and germination of the uredospores of Hemileia vastatrix, 

 F. C. voN Faber {Ber. Dent. Bot. GescU., 28 {1910), No. 5, pp. 138-141).— The 

 results are given of experiments on the germination and infection of the uredo- 

 spores of H. vn.siatrix under different light and moisture conditions. 



It was found that the spores germinated on both sides of the leaves, but that 

 infection occurred only on the undersurface through the stomata if moisture 

 was present. If \Aater remained long on the leaves the germ tubes did not 

 form appressoria, but branched and failed to enter the stomata. 



The .spores germinated in the dark as well as in the light, l)ut the germination 

 was favored by a short exposure to strong light. 



The outbreak of blister blight on tea in the Darjeeling District in 1908-9, 

 W. McRae (Agr. Jour. India, r, (1910), No. 2, pp. 12H-IS1. pis. 4. fig. 1).—X\\ 

 account is given of the first appearance, dissemination, and characteristics of 

 blister blight {E.rohnHidium rr.rans) in this district. 



In this disease the first indication of a blister is a small, pale green, yellow, 

 pink, or deep red circular sjtot which enlarges to a diameter of from 1 to 4 in., 

 forming a depression on the upper side of the leaf and a bulge on the lower 

 surface. The upper concave circular area Is smooth, shiny, and paler than the 



