750 , EXPERIMENT STATION RECORD. 



DISEASES OF PLANTS. 



Notes on plant diseases, T. W. Kirk {Neio Zeal. Dept. Agr. Ann. Rpt., 15 

 (]!I07), pp. J 'i 1-17 1, fl(/. 1). — Notes are given on a large number of diseases 

 which have been under observation, among them the diseases of sweet potatoes; 

 cherry leaf scorch, due to Onomonia erythrostoma ; diseases of garden plants, 

 vegetables, field and forage crops, and fruit crops; and bacterial diseases of the 

 pear, walnut, potato, cucumber, cabbage, hyacinth, and olive. 



Anu)ng the diseases of fruit crops one is mentioned which is said to have 

 been confused with the apple scab to a considerable extent. This is caused 

 by the fungus Coniothccium chomatosporum. The first visible indication of in- 

 fection consists of the appearance of minute cracks on the surface of the fruit. 

 This is followed by the gradual peeling off of the slvin in patches, giving the 

 affected apples a russetted appearaftce, somewhat resembling that sometimes 

 caused by Bordeaux mixture spraying. The tissues beneath the infected por- 

 tions harden and crack, resembling in general the appearance of apple scab, 

 but it may be distinguished by the absence of the velvety olive-colored patches 

 which are characteristic of the FusicJadium. The Couiothecium is said to 

 occur on leaves and twigs and probably winters over in cracks in the bark, 

 so that winter spraying with strong Bordeaux mixture or a lime-sulphur wash 

 is recommended. 



The cereal rusts, I. B. P. Evans (Ann. Bot. [London^, 21 {1901), No. 8.',, 

 pp. JiJil-lfGG, pis. //). — ^A detailed histplogical study was made of a number of 

 the more commoij cereal rusts and their biological forms to determine the 

 methods of attack by the parasite on the host plant, the subsequent growth of 

 the parasite, and the mutual relations of host and parasite. In the present 

 paper the attack of the parasite on the host plant is described. 



The author found two forms of attack. In the first the germ-tube emitted 

 from the spore penetrates the firm membrane or cuticle, this usually taking 

 place with the sporidia developed from the teleutospores. In the other case 

 the germ-tubes penetrate their host through the stomata, this method always 

 being adopted by uredospores and a?cidiospores. 



Each set of phenomena observed was found to be very definite for each 

 species, and the different species of Puccinia in the early stages of the uredo 

 mycelium exhibit morphological characters which serve to distinguish them 

 from one another. The substomatal vesicle has a definite shape for each 

 species, being nonseptate, septate, or even multiseptate, and giving rise to 

 one, two, or more infecting hyph*, according to the species. In some species 

 a well developed apjiressorium is pi-esent, while in others it is not so apparent. 



The vegetative hyplue of the different species closely resemble each other 

 in size and general behavior, except in the case of P. glmnarum, where they are 

 much thicker than any of the other forms and contain a much greater number 

 of nuclei. 



Tlie haustoria of some of the species are very distinctive, as is shown by the 

 hanuner-headed form commonly met with in P. symphyti-hromorum, whereas in 

 P. yhimanim, especially in the cells surrouuding the vascular bundles, they are 

 frequently bi*anched, while in the chlorophyll cells the typical form is that of 

 a small club-shai)ed body. 



The slight morphological differences between the mycelia of P. graminis on 

 wheat and P. phlci-pratensis are such as to be not worthy of specific charac- 

 terization. 



Seed infection by smut fungi of cereals, S. Hori (Bui. Imp.' Cent. Agr. 

 Erpt. Htd. Japan, 1 (1907), A'o. 2, pp. 163-176). — The author gives a summary 

 of five years' experiments to determiue the methods of iufectiou of cereals by 



