5o8 DISEASES OF CULTIVATED PLANTS 



In addition to the tea plant, the parasite is commonly 

 found on many trees in the jungle, more especially on those 

 having coriaceous leaves, where it occurs much more 

 frequently than on the branches. 



Dr. Mann emphasises the point that red rust is a disease of 

 weak plants, and that the primary aim of every planter who 

 wishes to check the disease should be to strengthen the 

 bushes, to seek out and deal with the causes of weakness 

 or otherwise every direct effort against the blight is bound 

 to fail. The same author gives a summary of the principal 

 conditions which may lead to an excessive development of 

 red rust. Hard pan in the sub-soil. Lack of cultivation. 

 Exhaustion of the soil. Susceptible type of plant. Unwise, 

 heavy pruning. Too close plucking in the early part of a 

 succession of seasons. Spraying with Bordeaux mixture 

 under certain circumstances. All those interested in the 

 cultivation of tea should become acquainted with Dr. Mann's 

 original paper on the subject. 



Cunningham, Trans. Linn. Soc. (Bot.), Ser. IL, i, p. 301 



(1879). 



Karsten, Ann. Jard. Bot. Buitenzorg (Java), 1891, pi. 4-6. 



Mann, H. M. and Hutchinson, C. M., Indian Tea Associa- 

 tion^ Ed. 2, No. 4 (1904). 



Marshall Ward, Trans. Linn. Soc. (Bot.), Ser. in., 2, p. 87 

 (1884). 



Watt, Sir George, and Mann, H. M., The Pests and Blights 

 of the Tea Plant, Ed. 2 (1903), 



Cephaleurus parasiticus (Karsten) is common on the leaves 

 of Calathea and Pandanus at Buitenzorg, Java. The epi- 

 dermal cells contain the alga, which spreads over the leaf, 

 blackening and killing it. 



Karsten, Ann. Jard. Bot. Buitenzorg, 10, i pi. (1891). 



Cephaleurus minus (Karsten) destroys the leaves of 

 Zizyphus jujuba, in Java. 



BACTERIA 



Until somewhat recently it was held, even by many 

 bacteriologists, that plants were practically free from diseases 

 directly due to bacteria. The general reason given was that 

 bacteria required an alkaline or at most a neutral medium 

 for their development, such as is generally met with in the 



