684 



functions and to the normal formation of chlorophyll by decrease of light 

 and heat; or by the increase of the nitrogen or potassium supply, thus pro- 

 longing the period of growth. 



A scanty supply of material frequently manifested in the increase of 

 tannin and the absence of starch, the small size of the cell and the increase 

 of the intercellular spaces, is also emphasized by Timpe in his carefully 

 worked out experiments. He describes a phenomenon for Ulmus which 

 seems strange to him but is exactly the best proof of our theory. In this 

 the luxuriant spring growth of shoots variegated with white developed per- 

 fectly green foliage after the tree had been set out; but the midsummer 

 growth, with a lack of water and excess of light and heat, again showed 

 the variegation*. 



If, however, albinism consists in the premature ending of hfe, i. e., in 

 the suppression, or arrestment, of the work of the chlorophyll apparatus, the 

 destructive enzymes, even if not increased in absolute amount, still obtain 

 a preponderance in the cell because those which cause the formation of the 

 reserve materials, have been too little developed due to the lack of chloro- 

 phyll activity. The equilibrium otherwise formed in the cells containing 

 chlorophyll is destroyed. 



We, therefore, do not need to assume the formation of a "virus" :■ — • 

 a group of materials acting poisonously, which must be produced and 

 increased in the plant, — in order to explain albinism and the phenomena of 

 disease related to it (the mosaic disease, shrivelling disease, etc.). It is 

 simply a change in the functions, i. e., a different direction of the mole- 

 cular motion to which we must trace back, however, all metabolic processes. 

 If this changed formation of substances is a movement, it can continue until 

 some other form of molecular motion causes its arrestment. II le non- 

 pigmented part of the plant is, therefore, the carrier of an abnormal motion 

 in its substances and on this account it would not seem strange if this motion 

 is continued as soon as the paths, i. e., the vascular bundles (according to 

 Pantanelli, the leptome parts), of two separated individuals are united, as 

 is the case in grafting. 



If we consider albinism not as a phenomenon coming from the ranks 

 of the othei" phenomena of variegation but only as the most extreme case of 

 a process representing a decrease in the amount of chlorophyll, it can no 

 longer seem strange that plants, variegated with yellow and, therefore, less 

 irritated, can still be brought to the production of seeds in which the same 

 direction of the metabolic motion is continued, i. e., that the seeds furnish 

 plants with yellow variegation. 



The Mosaic Disease of Tobacco. 



The most recent authors, who have w^-itten on albinism, have already 

 mentioned the relation of this phenomenon to the mosaic disease of 

 tobacco. 



* Loc. cit., p. 68. 



