440 



THE AMEBIC AX NATURALIST [Vol. XLIII 



from a part of the stem where the green tissue is covered by a 

 thin layer of white is itself constituted of green tissue covered 

 by white and produces ordinary white margined leaves. New 

 alhomarginate plants may thus be obtained from these marbled 

 seedlings by taking branches which thus arise from parts of the 

 stem where the white tissue forms a thin layer over the green. 

 The white margined plants are thus to be regarded as ' ' periclinal 



"White or green branches may arise from the white margined 

 plants as the result of irregularity in cell division at the growing 



The inheritance of the albomar<:inate character is now clear. 

 In a white mar-inn! plant pollen and ovules are produced from 

 white tissue only and hence carry only the white character. The 

 seedlings are therefore white. 



Sectorial chimeras were found in which the green tissue was 

 superficial and the white central, thus giving leaves that were 

 green on the margin and a paler color in the center, on account 

 of the white tissue in the center of the leaf. One of the plants 

 grown from a green branch occurritm on an albomaririnate plant 



The origin of the mosaic seedlings from a cross between white 

 margined and green is not yet fully clear. Careful study of 

 such of these seedlings as were recorded pure white revealed 

 indications of green tissue in the hypocotyls. Likewise, those 

 regarded as pure green revealed indications of white tissue. All 

 of the seedlings from the green-white cross are probably mosaics, 

 the differences being due to the fact that in some of them the 

 white tissue, in others the green, is confined to a few cells, the 

 remainder of the plant developing from the other tissue. 



It is important to note that in some of these mosaics, or mar- 

 bled plants, white "islands" may appear in several parts of the 

 plant. These islands are evidently not derived one from the 

 other. It can, therefore, be asserted that the differentiation of 

 these white cells occurs more than once during the development 

 of a plant and that the white cells must result from the division 

 of cells that are green in appearance. (It is important to re- 

 member that green is dominant in the cross.) Just when these 

 white cells arise can not be stated so positively. They may cer- 

 tainly arise after the formation of the cotyledons has begun. 



