1902 



VARIEGATION 



chromatophores, and the various 

 changes that these undergo, as the 

 leaf becomes older, produce the re- 

 markable and beautiful colorations 

 of this group of plants. The col- 

 oration liere, as in dracaenas and 

 caladiums, is iutensitied by strong 

 light and nourishing food. The 

 more of the modified chlorophyll 

 there is produced and the more 



chlc.v.i'l'^ll l„-..nL-lil : It il,r..ii-li 



the iiri, I l,_.l,l I il,,. nn.is 



•will lie tlie colors, though here 

 again high feedingis likely to cause 

 the plant to revert to its normal 

 coniliiioii. 



'1 [iliMii ■ (ir parts of 



pi. 



plants of 



generally il" i h\rl,,|, Mt;;iin 



branches. On ilf otlni hand, 

 when variegali |i\ili.|n in seed- 

 ally give a number of variegated 

 individuals, even the cotyledons 

 being sometimes affected. In 

 some cases the proportion of varie- 

 gited plants from seeds is Aery 

 large and can be mcreased hy selec 

 tion As a rule the form of spot 



rry 



itln 



yiA 



VARIEGATION 



plant, and causing the changes 

 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 

 iither t'ornis of or-iiinary variega- 

 ticiii, slii.w <niiti' i-nnehisively that 



i-titi-.il.-..n.liti.,n ,,f tlic nutrition of 



.i.taiU nl tl„. nitittir. it may be 

 <tii.l tlitit tiir !■,, million is charac- 

 t.-riziMl i.liysioli-iitully by amarked 

 increase in the oxidation processes 

 in the cells, caused by the presence 

 of an abnormal amount, or an ab- 

 normal 



foodsub.stanii :,,i , Ihs 



and nitrogeii-'ii iMini:.!, 'i'lu- 

 decrease of ilie Itut. r is is|,|.,i.-ii|y 

 marked, and it is pn.l.al.h cm ac- 

 count of the lack of sullinent ni- 

 trogenous food that llic cells do 

 not develop normally. The young 

 growing buds and dividing" 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, thon^l I i-iini' ...ii-iiiu- 

 ents of all c- I : \> iim 



they become ■ \. ■ . : . . tlie 



proper nutriiMi, < i i ; i.ling 



cells, and it is ;i ciiiiwii . i.,. i Ihat 

 when these ferments are eNir;ii-lc-d 

 from plant tissues and in.jic-lccl 

 into the young buds of lic-althy 

 tissues, they will, in the case of 

 tobacco at least, cause tlie buds sn 

 tieated to develop into variegtitc^cl 

 shoots. The ferment in 

 question passes readily 

 through the cell-walls of 

 ^^ — •. the plants and it thus he- 



y^\ comes evident how snch 

 ~V - > changes could be trans- 

 mitted by grafting and 

 budding, though no para- 

 sitic organisms of any kind 

 are connected with the 



Another method of producing 

 variegation of tobacco is by cutting 

 the plant back severely during 

 rapid growth. The new shoots 

 have to develnp I'lli :i -mi.iII sup- 

 ply of elaboriit. .: i 1, 



the larger ptnt : I in 



the severe vtm,: • -I ts 



thu 



beyond the normal amount, and 

 the reserve foods stored are in 

 small amount. 



These changes must, therefore, 

 he considered as pathological in 

 their nature, as the vitality and 



