REPRODUCTION 365 



While a reciprocal effect of the stock and the scion undoubtedly 

 exists, it must be, on the whole, insignificant. Thus, a score or 

 two of choice varieties of apples may be grafted into the crown of a 

 wild apple tree and each of them will preserve all its specific prop- 

 erties and will produce fruit of a quality characteristic of the spe- 

 cific variety. A preservation of the characteristics of a variety is 

 only possible because the reciprocal effects between the stock and 

 scion are very insignificant. 



Chimeras, which at one time were called "graft hybrids," 

 supply the most evident proof of the fact that each component of a 

 graft preserves its own specific properties in spite of their close 

 connection. They have been studied in detail by Winkler. By 

 chimeras are meant plants which are sometimes obtained as a 

 result of grafting one plant upon another and securing a combina- 

 tion of tissues of both. At first it was supposed that in these cases 

 a fusion of cells had taken place, similar to that occurring in fer- 

 tilization, hence the name "graft hybrids." Winkler's investiga- 

 tions, however, have shown that it is not so. He determined with 

 accuracy both the nature of chimeras and the method of obtaining 

 them. Chimeras are easily obtained from various species of 

 Solanum, especially Solarium nigrum and Solarium lycopersicum. 

 The latter may be joined to the former by cleft grafting. A stump 

 of the nightshade plant, Solanum nigrum, is split and into it is 

 inserted a wedge-shaped tomato scion. They are then left to 

 unite. When they have grown together, the scion is cut near the 

 union. This results in the formation of adventitious buds on the 

 cut surface. Those formed from the surface of the stump will 

 develop shoots of Solanum nigrum, while those arising from the 

 wedge will produce tomato shoots. Sometimes buds are formed 

 at the point of junction of the stock and scion, however, and then 

 they will develop into shoots of a combined nature. These will be 

 chimeras, in which one half of the tissues will belong to one plant, 

 the other half to the other. And if, for instance, the boundary 

 line passes across a leaf, the latter will be of an asymmetrical form 

 (Fig. 152, 2). Such chimeras are called "anticlinal." 



Winkler has obtained chimeras of a still more peculiar nature. 

 Sometimes the buds were so formed that the outward layers of the 

 growing points belonged to one plant and the inner tissues to 

 the other. As a result, all the organs developing from these buds 

 consisted of two kinds of tissues, the external tissues of one kind 



