i 3 o SCIENCE PROGRESS 



round for other plants which might proffer greater hopes of 

 positive results. In the first place, the subjects of experiment 

 must graft easily, and be readily reared in large numbers ; in 

 the second, they must have the property of producing large 

 numbers of adventitious buds from wounded surfaces. This was 

 of great importance, because he recognised that it was in new 

 buds arising from the graft, and not in the original scion, that 

 a modification was to be looked for. His studies in regenera- 

 tion enabled him to single out the most suitable plants, and 

 these he states are the poplars, the herbaceous members of the 

 Capparidacece, and the Solanums. His results were obtained 

 with these last. 



Briefly, the method employed is as follows. Two to three 

 month old seedlings of Solanum lycopersicum, the tomato, are 

 decapitated, and the apex of the stump is split open about a 

 couple of inches. Into this slit is inserted the wedge-shaped 

 end of the tip of a seedling of Solanum nigrum, the nightshade. 

 The two are bound together with bast, and kept moist and 

 poorly lighted, till the wounded surfaces have grown well 

 together, and the graft is complete. If left in this condition 

 the nightshade thrives excellently, and produces flowers and 

 fruits on the tomato stump. But if the system be again de- 

 capitated at the point of union of the two plants, and if the 

 precaution be taken to remove all the buds from the axils of 

 the leaves of the tomato stump, then, after about a fortnight, 

 a large number of adventitious buds develop on the cut surface. 

 If the decapitation has been performed at the proper point there 

 will be on the cut surface a small wedge of nightshade tissue, 

 grown firmly between the two halves of the tomato stem. 



Now all buds that developed on the tomato gave shoots of 

 pure tomato, and all buds that developed on the wedge of night- 

 shade gave pure nightshade. But in August 1907 Prof. Winkler 

 observed a bud which arose from a point on the line of junction 

 of the tissues of the two plants, and which developed into a 

 shoot of a unique character. The first leaf was a nightshade 

 leaf, and so were the fourth, fifth, and seventh leaves, and these 

 all arose from the side of the stem towards the wedge of night- 

 shade tissue ; but the second, third, and sixth leaves, which were 

 on the tomato side, were all tomato leaves ; and the eighth, 

 ninth, and eleventh, occupying positions opposite the line of 

 junction, were leaves of which one longitudinal half was tomato, 



