33 



Boucha^ made similar atatements concerning Plectogyne, Phal- 

 aris, Zea, Kerria, etc. Fortunately, we have had no thoro 

 . and reliable test of the question as to the influence ex- 

 ■ ercised hy the quality of the soil, the supply of water, 

 and of light on plants tending ^tovmrd variegation. The ques- 

 .tion also, whether the pecularity of the white leaved con- 

 dition may be carried over to normally colored specimens by 

 'scions or by inoculation with sap, has not yet been suffi- 

 (3^)ciently explained. The supposition of a "contagium vivium 

 fluidmn" which Beijerinck * had suggested, appears but little 

 suited for solving the problem. That unlinown individual 

 pecularities play a part in the appearance of v/hite leaved 

 plants, is made probable by the often observed seedlings free . 

 from chlorophyll which appear here aD.d there among those which 

 have become green normally. 



The effect of deficiency of light and iron is sufficient- 

 ly well kno\7n. In the dark, or rdthout "iron, pale plants are 

 produced which are capable of developing only a yellowish 

 colloring matter, instead of the normal green pigment* Accord- 

 ing to Kohlfs recent investigations,^ the yellow pigment is 

 to be designated carotin. The deficiency of normal pigment 

 in specimens cultivated in the absence of iron, is termed 

 chlorosis or icturus, with plants grown in darkness, it is 

 known as etiolation. In plants \-;hich grow in a substratum 

 containing iron, the ssrmptoms of chlorosis may also become 

 apparent if the cells of the plant or defp.nite parts of them 

 are incapable of taking up sufficient amounts of iron. The 

 chlorosis found in vines appears to be of this kind. :, •(.., 



' .1. Sitzungsber, Ges. Haturf, Freunde Berlin, 1870,. .... 

 p. 40 and 1871, p. 19, 6^. Compare here also Lindemuth. 

 Vegetative Bastarderzeugung duroh Impfung. Landv;irtsch. 

 Jahrb,,. 1878, Bd, VII, p., 887. 



£• tJeber e.in contagium vivum fluidum als Ursache der 

 Fleckenkrankh. der Tabaksblatter. Centrabl, f . Bakteriol 

 ;',,^:. etc. ," 1899.," 2. Abth. Bd, V,.p. 27. Further, the attempt at 

 ' explantation; made by Woods should be mentioned, (The des- 

 truction of chlorophyll by oxydizing enzymes. Ibid., p. 745), 

 which- calls attention to the richness of variegated leaves 

 in .oxydizing enzymes and to the action of these in destroy- 

 ing-chlorophyll. The same author published- ")bservations on ■. 

 the'.Mosaid. disease of tobacco" (United States Department of 

 Agriculture, B. P- ID. Bull',' No. , 18,, 1902). .The oxydizing 

 enzymes prQduced after injury, as well as under. the influence :.. 

 of poisons after parasitic .infection will have great signi- 

 ficance undoub'tediy for the pathology of plant cells .and tis- 

 sues, , (Compare" besides Janowski in Ztschr. f, Pfl.w Krai^. 

 190E, Bd, .XII, p. 202.) . ■ 



3.. tJntersuchungen Uber das Carotin und .seine plys. 

 Bedeutung in der. Pfl. Leipzig. 1902. 



