1902 



VARIEGATION 



VARIEGATION 



1j 



tl 



chromutopbores, and the vuriouw 

 changes that these undergo, as the 

 leaf becomes older, produce tbe re- 

 markable and beautiful colorations 

 of this group of plants. The col- 

 oration here, as in dracipuas and 

 caladiums, is intensitied by strong 

 light and nourishing fond. Thr 

 more of the modified clilorophyl 

 t h ere is pr( »d need an d th e n i (iri- 

 rajnd tbe changes in the modified 

 chb.r(.|)1jyll lifnught about tlirough 

 the action of light and the acids 

 and nxidizinLj" fi-rn)euts of the 

 leavL's, till- nuirt.-' lli^hly developed 

 will bi^ thr (-(ijors, tbongh here 

 h feedin^j; is likely tc cause 

 to reVfii. X>> its normal 

 ci>ndilion. 



Varii-gati-d ]ihints or parts of 

 pbtiits ;ii''- Usually of sIow.t i^rowtli 

 and sinalb-r Than -rocn plants of 

 the same variety or the green parts 

 of tbe same i>lant. 



CdHs.s of \'uri,ii<ili.>,i. -\'arie- 

 gation occurs c-itbi-r iiy bud-\'aria- 

 tion or by vai-iatinns in soiMllings. 

 In till- f'lrnnT. a va r-ir^ati-d hranch 

 is likrly to a|i]H-ar (^i an ntln-rwise 

 pi-rfertly normal plant. Sncli ^-arie- 

 gatioiis aro easily ro] trod need by 

 bnddiiiL:. grafting or cuttings, but 

 generally <lo not develop again 

 f fom seeds ii r o d ii e e (.1 on smdi 

 branches. On the other hand, 

 when variegation develops in seed- 

 lings, the seeds of such plants usu- 

 ally give a number of variegated 

 individuals, even the cotyledons 

 being son;ietimes affected 

 some cases the proportion of varie- 

 gated plants from seeds is very 

 large and can be increased by selec- 

 tion, •- As a rule, the form of spot- 

 ting or marking i"^ not constant in 

 seedlings, often Vieing very differ- 

 ent from lIic parent. In certain 

 groups of plants, which 

 have for many years been 

 selected on account of 

 the horticultural value <^i 

 these markings, the 

 variegated condition has 

 lieconie almost a hxed 

 feature of the plant, as 

 in dracienas, caladiums, 

 codifeums, etc. While 

 the plants of these genera 

 are not usually propa- 

 gated from seeds, still 

 when they are so propa- 

 gated, a large number of 

 seedlings show more or less varie- 

 gation. 



Darwin and many of the earlier 

 investigators believed that these 

 variations were started in the 

 jdant by unfavorable nutritive con- 

 ditions, and much has been written 

 on tlie subject as to whether or not 

 variegations should be considered 

 as diseased conditions. 



The question as to wl 

 variegated condition co 

 transmitted to normal ]i 

 budd i n g and g'"ra f ti n g 1 

 been much disputed, buttl. 

 of evidence indicates that in manv 

 cases such transmission certainly 

 fakes idace. This has been thougli't 

 to indicate the presence of some 

 viiirro-nriranisiii, living eitlier pai'a- 

 sil ically or svnibioticallv in the 



ether a 

 Hild bo 

 hints by 

 ;is also 



■ weight 



Kinds of 

 above an 



varicjiratinn. Sanscvieria 

 d Caladium below. 



plant, and causing the 

 known as variegation. 



Investigations conducted by the 

 ■writer on the so-called mosaic dis- 

 ease of tobacco, which is a form 

 of variegation, and also on many 

 other forms of ordinary variega- 

 tion, show quite conclusively that 

 the disease is not caused by micro- 

 organisms, but is due to a de- 

 ranged condition of the nutrition of 

 the cells. Without going into the 

 details of tbe matter, it may l)e 

 said that the condition is charac- 

 terized physiologically by a marked 

 increase in the oxidation processes 

 in tilt:' cells, caused I»y the j")resence 

 of an almormal anjount, or an ab- 

 normal activity, of oxidizing fer- 

 ment in the protoplasm. This fer- 

 ment prevents the movement of 

 food substances, especially starches 

 and nitrogenous materials. The 

 decrease of the latter is especially 

 marked, and it i.s pndjably on ac- 

 count of the lack of sufticient ni- 

 trogenous food that the cells do 

 not develop normally. The young 

 growing buds and <lividing cells 

 require highly organized albumi- 

 noid foods. They do not make 

 use, to any extent, during the pro- 

 cess of growth and cell division, 

 of the ordinary nitrates which are 

 built up into nitrogenous foods by 

 the mature cells. The oxidizing 

 ferments, though normal constitu- 

 ents of all cells, prevent, when 

 they become excessively active, the 

 proper nutrition of the dividing 

 cells, and it is a curious fact that 

 when these ferments are extracted 

 from plant tissues and injected 

 into the young buds of healthy 

 tissues, they will, in the case of 

 tobacco at least, cause the buds so 

 treated to develop into variegated 

 shoots. The ferment in 

 question passes readily 

 through the cell-walls of 

 the plants and it thus be- 

 comes evident how siich 

 changes could be trans- 

 mitted by grafting and 

 budding, though no para- 

 sitic organisms of any kind 

 are connected with the 

 matter. 

 Another method of producing 

 variegation of tobacco is by cutting 

 the plant back severely during 

 rapid growth. The new shoots 

 have to develop with a small sup- 

 ply of elaborated nitrogenous food, 

 the larger part being removed in 

 the severe cutting back. Shoots 

 thus developed nearly always show 

 variegation. The same thing is 

 true of many other plants, espe- 

 ciallythe potato, tomato, mulberry, 

 etc. In fact, it appears that a 

 plant is likely to show vaidegation 

 whenever it is so treated that the 

 growing buds or the forming buds, 

 or the seeds, have to devtdop un- 

 dersuch conditions that the ferment 

 content of the cells is increased 

 beyond the normal amount, and 

 the reserve foods stored are in 

 small amount. 



These changes must, therefore, 

 lie considered as pathological in 

 their nature, as the vitality and 



