328 GENERAL PLANT PATHOLOGY 



BuNZEL, Herbert H. : The Measurement of the Oxidase Content of Plant Juices. 



Bull. 238, Bureau of Plant Industry, U. S. Dept. Agric., 191 2. 

 Chapman, G. H. : Mosaic and Allied Diseases with Especial Reference to Tobacco 



and Tomato. 2sth Annual Report Mass. Agric. Exper. Stat., 1913: 94-104. 

 Clinton, G. P.: Chlorosis of Plants with Special Reference to Calico of Tobacco. 



Report Conn. Agric. Exper. Stat., New Hav^en, 1914: 357-424, with 8 plates. 

 Kastle, J. H. : The Oxidases and other Oxygen Catalysts concerned in Biological 



Oxidations. Bull. 59, U. S. Hygienic Lab., 1910. 

 Klebahn, Professor Dr. H.: Grundziige der Allgemeinen Phytopathologie, 



191 2: 124-127. 

 Woods, Albert F.: Observations on the Mosaic Disease of Tobacco. Bull. 18, 



Bureau of Plant Industry, U. S. Dept. Agric, 1902. 



Nutritive disturbances may also be included as internal causes of 

 disease. If for any reason, such as the inability of the living cells of 

 the root to take up water through a change in the osmotic power of the 

 protoplasmic membrane of the root hair cells, the leaves above owing 

 to active transpiration cannot secure sufficient quantities of water 

 and the whole plant wilts. A disturbance in the formation of starch 

 in the chloroplast results in a deficiency of the plastic carbohydrates, 

 and the active cells of the cambium during this period of starvation 

 form less wood and, therefore, fewer conducting vessels. This reacts 

 on the tissues everywhere in the plant by reducing the available water 

 and food and, therefore, the plant is dwarfed and perhaps sickly. 

 Intumescences are trichomatous outgrowths not associated with 

 insects or fungi which are due to some disturbance of the balance 

 between transpiration and assimilation. 



Mutations which result in the sterility of an annual species would 

 lead to the extinction of the plant with such non-seed production. 

 (Enothera albida is a pale-green, rather brittle and very delicate form 

 with narrow leaves; never attaining anything like the height of (E. 

 Lamarckiana. It bears pale flowers and weak fruits which contain 

 little seed. It appears every year in most of de Vries's cultures in 

 larger or smaller numbers. The plants are so weak that de Vries 

 imagined them to be diseased,^ and after much difficulty he secured 

 seeds from them. Enough has been given on these points to show that 

 mutations may be along the line of plants constitutionally weak. 

 The absence of amygdalin and prussic acid in the Sweet Almond 

 may make such a form more susceptible to disease, as also the absence 

 of quinine from cinchona trees kept in European hot houses. 



^DE Vries, Hugo: The Mutation Theory (English edition), I: 229, 1909. 



