56 EXPERIMENT STATION RECORD. 



In his conclusions the author states that the olive knot disease is at 

 presenl limited to a very small range in California, but as it promises 

 to be very harmful in some localities special precautions should betaken 

 to prevent its spread. The conditions which favor the growth of the 

 organism arc delicacy of tissue owing to vigorous growth or variety, 

 high sap pressure, wounds, and hot weather. Various precautions are 

 suggested to he observed, in pruning and earing for trees lest the dis- 

 ease may be spread. The author believes that olives from diseased 

 trees are perfectly wholesome and may be used for oil purposes unless 

 the vitality of the tree is seriously affected, but that the fruit is prob- 

 ably useless lor pickling. 



A destructive disease of maize, M. Kaoiborski (Ber.Deut. Bot. 

 Gesell., 15 (1897), No. 8, pp. 475-47S,pj. J).— The author reports the 

 occurrence in Java of a very destructive disease of maize due to au 

 apparently undescribed fungus, Peronospora maydis. 



The disease attacks the young plants, the first two or three lea ves 

 appearing healthy, but the subsequent ones becoming white or very 

 light green. Later the leaves change to such a degree that the white 

 spots may be seen at quite a distance. The appearance of the discolored 

 leaves is followed by the wilting and death of the plants. Exam- 

 ination of I he diseased leaves showed the presence of a uniseptate 

 mycelium which bears very numerous haustoria. Through the stomata 

 appear the conidiophores, which are 3 mm. high, 25 // in diameter, and 

 from 3 to <> times diehotomously branched. The conidia are spherical, 

 l."» to 18 n in diameter, and germinate in a. few hours, producing one or 

 niorehyphse. Culture experiments showed that the conidia when inocu- 

 lated upon the leaves of maize produced the characteristic spotting 

 within twelve to eighteen days after the first iutection. The oogonia 

 are L8 to 25 /i in diameter, with a not very thick but resistant membrane, 

 which hears a few small, conical thickenings. 



While the disease is evidently spread by the conidia being blown 

 about by the wind, the author thinks the oospores in the soil the chief 

 method of infection. The usual practice of alternating sugar cane and 

 maize would tend to increase the liability to disease through the pres- 

 ence of innumerable oospores in the soil where the young maize plants 

 have grown. 



Thus far the disease i^ known on/y from Java, and it is thought pos- 

 sible that the fungus may have been introduced upon the maize from 

 some of the native grasses. The introduction of the disease into the 

 great maize growing countries would be deplorable. 



The diseases of the sugar cane in Java, J. H. Wakker and 

 F. A. P. C Went (De Ziekten ran het SuMcerriet op Java. Leiden: 

 /•:. J. Brill, 1898, pp. 217, pis. 25).— The authors describe, figure, and, 

 where known, give remedial measures for the various diseases to which 

 sugar cane in Java is subject. The diseases are grouped into four 

 classes, those of the stalk, leaf sheath, leaf blade, and root. In addition, 

 the gummosis of the sugar cane is discussed. 



