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The Journal of Heredity 



of these intermediates or periclinal 

 chimeras is shown in The Journal of 

 Heredity, Vol. 5, No. 12, and an excel- 

 lent discussion of how such chimeras 

 are produced is there given. 



Similar study of Cytisus Adami and 

 the Crataegus- Mespilus so-called graft- 

 hybrids showed that they are also 

 periclinal chimeras with one or more 

 cell-layers of one species covering a 

 body of cells of the other species. 



INTERACTION OF DIFFERENT KINDS OF 



CELLS 



The rather intimate association of 

 the cells of two different species in the 

 same stem, leaf, flower, and fruit is 

 especially interesting in view of the 

 mutual interactions, mechanical and 

 physiological, that may occur. The 

 evidence indicates that the two kinds 

 of cells remain independent in respect 

 to their own hereditary characteristics, 

 but in the periclinal chimera they 

 interact producing organs that are 

 intermediate in character. Slight dif- 

 ferences in the arrangement of the 

 same two kinds of cells also produces 

 vegetative and floral structures and 

 fruits that are quite different in 

 appearance. 



While the investigations indicate 

 that the supposed graft-hybrids are 

 in nature only periclinal chimeras, the 

 production of true graft-hybrid through 

 a fusion of vegetative cells is still to 

 be considered possible. In fact Dr. 

 Winkler has presented evidence that 

 this is the case in one adventitious 

 branch that arose from a decapitated 

 graft between the tomato and the 

 nightshade. 



The production of sectoral and peri- 

 clinal chimeras by experimental means 

 readily shows how such branches can 

 arise incidentally on plants grafted by 

 the ordinary methods. New and 

 adventitious buds may arise from the 

 region of union between stock and 

 scion, especially if the upper part of 

 the scion dies. If such a bud arises 

 over the line of contact it may develop 

 as a chimera. Dr. Winkler's studies 

 show that sectoral associations develop 

 more frequently than do the periclinal. 



CHIMERAS THROUGH BUD SPORTING 



It should be noted that intra-varietal 

 sectoral and periclinal chimeras fre- 

 quently arise through bud sporting. 

 Such partial bud sports have been 

 described frequently in the pages of 

 this journal, especially for such 

 conspicuous cases as the loss of green 

 color which is carried on into various 

 new branches. 



Some of the albomarginate types of 

 variegated plants (of Pelargonium for 

 example) are clearly periclinal associa- 

 tions of green and white cells all of 

 which belong to the particular variety. 

 In the original sport, most probably, a 

 single cell lost the ability to produce the 

 green pigment and this cell was so 

 placed in the growing point that its 

 multiplication by division gave one or 

 more layers of white cells. Once 

 established the relative position of the 

 white and the green cells was main- 

 tained rather uniformly in the subse- 

 quent development of branches. 



It is also to be noted that, in many 

 sorts of variegated plants, though the 

 pattern strongly simulates a chimeral 

 arrangement, it is really due to physio- 

 logical conditions affecting develop- 

 ment of color in the leaf as a whole. 

 In these the colored and colorless 

 areas often cut across cell layers or 

 histogens. Much remains to be 

 learned regarding the development of 

 such local areas of infectious chlorosis, 

 as well as the development of various 

 patterns of anthocyanin coloration in 

 flowers and foliage. 



PROBABLE ORIGIN OF THIS CHIMERA 



Mr. Whitney's tree bearing Russet 

 and King fruits is evidently a chimera 

 that has grown from a bud that arose 

 on the line of contact between scion 

 and stock, and is hence to be considered 

 as a graft-chimera. Presumably a 

 scion of King was grafted to the root 

 of a seedling of the Russet in the 

 method of ordinary nursery practice. 

 At any rate the tree is clearly an inter- 

 varietal chimera: some branches are 

 composed of sectors of tissue of two 

 varieties; lateral branches arising from 



