DISEASES OF PLANTS. 157 



water thus formed dissolving some of the copper, which then diffuses through 

 the water film into the stomatic chamber where it kills the cells with which it 

 comes in contact. 



On the outbreak of red leaf spot in the vineyards of Griinberg in Silesia, 

 G. LtJSTNER {Ber. K. Lehranst. Wein, Ohst u. Gartenbau Geiscnheim, 1909, pp. 

 126-129, fig. 1). — It is stated that the disease has been present in this region 

 for over 100 years, being worse during some seasons than others. 



It appears as reddish spots or streaks at the junction of the main and side 

 veins or of two side veins, and often spreads over a great part of the leaf 

 surface. Later the affected tissues turn a clear dark brown color, and finally 

 the diseased leaves fall off. 



The disease is caused by a fungus (Pseudopeziza tracheiphila) , which lives 

 in the vessels of the leaf veins. It is usually associated with sandy or gravelly 

 .soils where the rain water sinks too rapidly, so that the vines in dry weather 

 suffer for lack of moisture. 



The addition of vegetable matter, manure, etc., to such soils is suggested as a 

 probable remedy. 



Stereum hirsutum as a destroyer of grapevine stakes, G. LtJSTNER (Ber. 

 K. Lehranst. Wein, Ohst n. Gartenbau Geisenheim, 1909, pp. 133, 134, fi9- 1)- — 

 In addition to the two known stake destroying fungi (Polyporifs vaporarius and 

 Xylaria Jiypoxylon), the author claims that S. hirsutum also rots the grapevine 

 stakes (usually oak), making them brittle and easily broken off at the ground. 



On the structure and life history of Diplodia natalensis n. sp., I. B. P. 

 Evans {Transvaal Dept. Agr., Sci. Bui. Jf, pp. 18, pis. 8; ahs. as Transvaal Dept. 

 Agr., Farmers' Bui. 109, pp. J,, fig. i).— This is a further report (E. S. R., 23, 

 p. 550) on the black rot of Natal citrus fruit, including a discussion of its 

 general and specific characteristics, means of dissemination, methods of com- 

 bating it, and the systematic position of the causal organism, D. natalensis. 



It is claimed that the fungus is able to attack citrus fruit in all stages of 

 development, provided the fruit is plucked or the rind slightly injured, but that 

 the infection usually occurs at the stem end of the fruit and may remain 10 

 to 15 days before any signs of the disease appear. It also attacks apples, apri- 

 cots, and peaches through abrasions in the skin. 



The disease is carried over from season to season by means of the fungi 

 present on mummified fruits lying about the orchard. 



Cleaning up the orchard and burning all fallen fruit is recommended as a 

 remedy for controlling the disease. 



The diseases of the orange, G. Gandara {Estac. Agr. Cent. [Mexico] Bol. 

 31, pp. 1-17, 43-51, pis. 16). — In a discussion of plant and animal parasites of 

 the orange in Yucatan, the author figures and describes the characteristics of 

 each and gives methods of combating them. 



In the first part devoted to plant parasites of the orange, the following are 

 noted: Gummosis (Bacterium gummis) ; anthracnose (Colletotrichum glceo- 

 sporioides) ; fruit spot (Glceosporium psidii) ; verrucosis (Cladosporium sp.) ; 

 canker (Dematophora necatrix) ; wiiite crust caused by a Corticium which 

 grows on the extremities of the branches, completely killing them, for which 

 cutting and burning the infected limbs is the only remedy suggested; three 

 polypori (Polyporus hispidus, P. annosus, and P. igniarius) ; a fungus parasitic 

 on the large roots and trunks of the orange trees, belonging apparently to the 

 family, Tremelinacese; dodder (Cuscutaamericana) ; "moss" {Tillandsiarecur- 

 vata) ; and mistletoe (Loranthus ealyculatus). 



In the second part the diseases due to animal parasites are discussed (see 

 p. 163) . In the third part, the diseases due to physiological causes are described, 

 viz, chlorosis, and a splitting of the fruit. The fourth part discusses diseases 



