No. 529] THE NATURE OF OR AFT -HYBRIDS 



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erer felt warranted in assuming that these were really 

 hybrids, probably arising from the actual fusion of cells 

 derived respectively from the nightshade and the tomato, 

 this fusion taking place where the graft had united with 

 the stock. This cell-fusion was assumed to involve a 

 fusion of the nuclei as well, analogous to the fusion of the 

 egg-nucleus with the generative nucleus of the pollen 

 tube in normal fertilization. 



Several types of these graft-hybrids were produced 

 and to these specific names were given. 



The first genuine graft-hybrid was called Solanum 

 tubingense and it has since been produced several times 

 and has been propagated by cuttings and distributed to 

 various botanical gardens. During the past summer I 

 had an opportunity of seeing this graft-hybrid growing 

 well in the botanical gardens of the University of Munich. 



Solanum tubingense is intermediate in external appear- 

 ance between the nightshade and tomato but is rather 

 nearer the former (see Fig. 1, C). The nightshade {A) 

 has simple, smooth-edged, oval leaves and an almost 

 smooth stem. The tomato (B) has compound leaves with 

 sharply serrate leaflets and all of the varieties are 

 strongly hairy. The hybrid (see Fig. 1, C) has simple 

 leaves but they are sharply serrate or often slightly lobed 

 like the leaflets of the tomato, and both stem and leaves 

 are abundantly provided with hairs. 



The flower in Solanum tubingense is also intermediate 

 in character. The nightshade has small white flowers 

 with a smooth calyx whose lobes are very short. The 

 flower of the tomato is much larger, bright yellow in 

 color and the lobes of the calyx are hairy and very much 

 longer than those in the nightshade. The hybrid has 

 flowers which are intermediate in character. They are 

 larger than those of the nightshade but much smaller 

 than those of the tomato, but like the latter the flowers 

 are a pronounced yellow. The calyx lobes are two or 

 three times as long as those of the nightshade but much 

 shorter than those of the tomato. Like the latter, how- 



