CAUSES OF DISEASE. 107 



referred to in the last chapter. Also Kirchner, Pflanzen 

 Krankheiten, Stuttgart, 1890. 



Of more historical importance are the older classifications 

 of Berkeley, Gardeners' Chronicle, 1854, and Re, Gardener^ 

 C/irotiiclc, 1849-50. These latter are interesting as showing 

 the very different views held by the earlier workers, and com- 

 parison of these with the modern views helps to mark the 

 progress of physiology during the half century which has 

 intervened. 



