376 GENETICS IN RELATION TO AGRICULTURE 
nightshade. But sufficient evidence of their mixed composition is found 
in the character of their progeny and from the study of chromosome 
numbers made by Winkler. In tubigense the fruits are almost identical 
b 
i) OD 
Fig. 152.—Diagrams showing methods of grafting used in producing the tomato- 
nightshade chimeras and some of the results; shaded portions represent scion tissue, Un- 
shaded, stock tissue. a, Splice graft; b, cleft or wedge graft; c, saddle graft; d, sectorial 
chimera (shaded portion, nightshade; unshaded portion, tomato tissue); ¢, chimera leaf, 
part nightshade, part tomato; f, nightshade; g, periclinal chimera, Solanum tubigense; 
h, Tomato. (After Winkler from White.) 
with those of the nightshade and the seeds produce only pure nightshade 
plants. The reason for this is clear when it is remembered that this 
form is really nightshade with a single epidermal layer of tomato cells, since 
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