Stout: Bud-variation in Pelargonium 371 



like those which are borne on the branches that are composed 

 purely of green tissue. When the white is outside, the leaf is 

 much smaller and more like those leaves which are composed only 

 of white tissue. Several plants of Pelargonium Madame Salleroi 

 of the same clone as the plant producing this bud-variation have 

 been under observation in the propagating houses. Several of 

 these have produced leaves composed wholly of white cells. These 

 have been of practically the same shape and size as the variegated 

 leaves on the same plant. The pure white cells are, of course., 

 dependent upon the green cells for carbohydrate food. In the 

 case of a chimera relationship with the green cells enclosed, there 

 may be mechanical and chemical stimuli to the overlying white 

 cells that result in a slightly larger leaf. This effect is, however, 

 not marked. 



All the potentialities of a large and deeply lobed leaf are present 

 in the green cells of a typical leaf of the Madame Salleroi variety. 

 When these green cells get to the exterior those potentialities find 

 expression, but as long as the peripheral layers of white are uni- 

 formly maintained, there is no visible evidence that these poten- 

 tialities exist. Their suppression may be due chiefly to mechanical 

 limitations imposed by the peripheral layers of white cells which 

 decrease the number of cell divisions. 



In the various plant chimeras there is an association of more or 

 less independent and different kinds of cells. In the chimeras 

 resulting from grafting, the two kinds of cells may be decidedly 

 different, producing, when separate, two distinct types of leaves, 

 but when associated together, forming leaves of still different 

 patterns. The various chimeras produced by Winkler (1907 and 

 1909) and the chimera Crataegomespilus Asnieresii (see illustration 

 by Baur 191 1, pi. VIII) illustrate this phenomenon. In addition 

 to such mechanical and physical interactions, Winkler (19 10) has 

 presented some evidence that there may be a vegetative fusion of 

 cells in graft tissues producing what he would consider as the only 

 true graft-hybrid, and he further holds that hybrid modifications 

 may also result from the migration of such substances as atropin or 

 nicotine between stock and scion. 



These facts indicate that the general phenomena of plant 

 chimeras have a very direct bearing on theories of morphogenesis 



