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. 47A, 6b), the pollen mother cells 
contain the reduced number of chromosomes 
(Fig. 47A, a). The tissue cells of the giant con- 
tained 48 chromosomes (Fig. 47A, d), and the 
pollen mother cells 24 chromosomes (Fig. 47A, 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 that 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 
