682 



If the supply to the young cells is cut off too soon, because the material, 

 increasing the amount of protoplasm, is supplied too scantily, and the cell 

 wall becomes old prematurely, the cell can have performed only the first 

 part of its task, the formation of the wall, and has nothing left over for the 

 formation of the apparatus which produces reduction and increases the dry 

 substances, nor for its maintenance. This same poverty must occur in the 

 normal cell if it gets into conditions of growth which cause an accumulation 

 of destructive, i. e., amylolytic enzymes, whereby it is again carried back 

 toward the young stage. If the plant is brought under conditions which 

 favor normal vegetative activity (shade, moisture and heat) the non-pig- 

 mented parts of the axis tend to produce green leaves. A discovery of 

 Lindemuth's confirms this observation. He proved that intense light actu- 

 ally favors albinism. Ernst^ mentions that in Caracas Solanus aiigerum 

 Schlecht., common to that region, is found not infrequently with variegated 

 leaves. This occurs, however, only on poor soil. Specimens with stroayly 

 variegated leaves, transplanted to better soil, become green. With Urtica 

 dioica, Beijerinck-, even in one year, succeeded in bringing back the green 

 form from the variegated form by means of cuttings. 



Tissues, with a less concentrated cell sap are, however, less resistant. 

 Actually, the white leaved parts of the plants are more sensitive to heat, 

 frost, and drought, and die sooner. We find more abundant examples in 

 the white leaved Acer Negundo, in which even the bark of the branches 

 becomes variegated. Almost every year, summer sunburn and winter frosts 

 kill the most exposed branches. Such cases also occur in conifers\ In 

 the same way seedlings with white cotyledons and plumules are very easily 

 destroyed. Not infrequently I have found pure white seedlings, or white 

 ones with a reddish tinge, in larger sowings of various kinds of fruits. 

 These were always treated with special attention but died after some time, 

 in case they did not begin to produce green leaves. Similar observations 

 have been made also by others, for example, on Phormium tenax (de Smet), 

 Passiflora quadrangularis as well as on Dahlia variabilis, Dianthus Caryo- 

 phyllus, and the Liliacea (Lindemuth). A scarcity of reserve substances 

 in non-pigmented branches explains also the further observation that their 

 cuttings grow with greater difficulty than those from the green parts of the 

 same individual. Consider, for example, hydrangeas with pure white 

 leaves and geraniums from the group "Miss Pollack." 



Lindemuth observed in Abutilon that the non-pigmented leaves are 

 usually smaller and have a shorter life period. We would recall in this 

 connection the phenomenon, occurring not infrequently, in our wild plants, 

 that when one-half of the leaf is white, the other half green, the former 

 remains shorter and the latter, on this account, curves about the white half 

 in the form of a sickle. (Cichorium, Beta.) In marbled leaves, the white 



1 Botanische Miscellaneen. Bot. Zcit. 1876, p. 37. 



2 Beijerinck, M. W., Chlorella variegator, ein bunter Mikrobe; cit. Bot. Cen- 

 trabl. G. Fischer, 1907, p. 333. 



3 Zeitsch. f. Pflanzenkrankh. 1896, p. 361. 



