178 • THE CHROMOSOMES 



(periclinal chimaera), or a bud with the reverse 

 relations, namely, nightshade core and tomato skin. 

 Still another kind of bud also rarely arose, namely, 

 one that was tomato on one side (or in one section) 

 and nightshade on the other (sectorial chimaera). 

 In one instance a periclinal chimaera arose that was 

 a giant, and which Winkler showed was tetraploid. 

 It had a core of .tomato cells that were tetraploid, 

 and a skin of nightshade. Winkler got rid of the 

 skin by cutting the stem of a young plant across 

 and removing its axial buds. The adventitious buds 

 that developed from the callus over the cut end 

 were in some cases composed entirely of tomato 

 cells, both in core and skin. Such plants were 

 pure tetraploid giants. 



• The cells of the ordinary tomato contain 24 chro- 

 mosomes (Fig. 47^1, b), the pollen mother ceUs 

 contain the reduced number of chromosomes 

 (Fig. 4:7 A, a). The tissue cells of the giant con- 

 tained 48 chromosomes (Fig. 47^, d), and the 

 pollen mother cells 24 chromosomes (Fig. 47 A, c). 

 How the original doubling of the number of the 

 chromosomes comes about in cases like this one is 

 unknown. It may have arisen by two cells fusing 

 at the cut surface into a single cell fhat formed the 

 growing tip of a new plant, or a tetraploid cell may 

 have arisen by a direct doubling of the number of 

 chromosomes in a cell as a result of the failure of 

 the cell to divide after the chromosomes had divided. 

 Since giants never appeared from a callus or from 

 adventitious buds, except in cases where grafting 



