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 



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; 6, cleft or wedge graft; c, saddle graft; d, sectorial 

 chimera (shaded portion, nightshade; unshaded portion, tomato tissue); e, chimera leaf, 

 part nightshade, part tomato; /, nightshade; g, periclinal chimera, Solatium 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 



