The Editor: Plant Chimeras 



531 



HOW THE GREEN CELLS ARE OVERLAID BY WHITE 



Highly magnified cross section of parts of geranium leaves, after Baur. At the top of each 

 one is seen a colorless layer of cells forming the epidermis, and common to all geraniums. 

 (a) represents a variegated geranium; below the epidermis is seen a single layer of almost 

 colorless cells which come from a white plant. They are found not only at the surface 

 of this leaf, but of all the other leaves and stems of the plant. Below this layer of white 

 cells is the mass of green cells, bearing chlorophyll granules, which make up the body 

 of this variegated plant, (b) shows part of the leaf of an ordinary green geranium. There 

 are no white cells, the whole plant being made up of green tissue. The essence of a chimera 

 is that it be composed of tissues from two different plants. (Fig. 9.) 



pollen grains and ovtiles from all the 

 new Solanums eagerly counted, with 

 the expectation or at least the hope that 

 the number found would be either 48 or 

 96. But the only counts secured were 

 either 24 or 72; each chimera possessed 

 the chromosome count of the parent 

 which it most resembled, just as it re- 

 produced that parent by seed. 



ARE THE CHIMERAS HYBRIDS? 



In the face of such results, the Solan- 

 ums which Winkler had created with so 

 much difficulty could hardly have 

 ranked as hybrids of any kind, had not 

 Baur's work showed the ingenious and 

 unexpected way in which the two par- 



ents actually entered into the progeny, 

 by the hand-in-glove method. As far 

 as the evidence from breeding and from 

 chromosome counts went, they would 

 have had to be thrown out of the hybrid 

 class; and this perhaps is the proper 

 course after all, in spite of the fact that 

 they are undeniable graft-hybrids, in 

 the broadest sense of the term. If they 

 are merely designated as chimeras, the 

 term hybrid can be reserved for plants 

 which more completely share the germ- 

 plasm of their parents, and confusion 

 will thereby be obviated. 



But there is one more chimera, which 

 was alluded to near the beginning of this 

 paper and has since, for the sake of 



