Ways in Which Plants Increase in Size 351 



From the facts just stated, it would seem impossible for graft 

 hybrids, that is, intimate mixtures of the protoplasm of stock and 

 scion, to exist. Yet graft hybrids have actually been claimed to 

 occur, though very rarely. And here opens up one of the most 

 interesting chapters in recent experimental studies, for it has been 

 found possible to produce experimentally such apparent graft 

 hybrids. But the very same experiments have shown that they 

 are really not hybrids at all, but merely mixtures of the tissues of 

 the scion and stock, and not a blending of their protoplasm. These 

 experiments were made by grafting a part of a bud of the scion to 

 a part of a bud of the stock, when the resultant branch displayed 

 a most remarkable mixture of the colors, shapes, tissue characters, 

 and other features of scion and stock — not a blending but a 

 mixture. Sometimes the upper side of the branch would be all 

 scion with the characters thereto appropriate, and the under side 

 all stock; sometimes a sheath of stock enwrapped a core of scion; 

 and other mixtures of other sort occurred. Such graft products 

 are not hybrids, and have been named chimceras. But are graft 

 hybrids then impossible? Theoretically they are not, for if one 

 cut cell of the stock and one cut cell of the scion should happen to 

 match together, and if then their two nuclei should fuse together 

 (as they well might, for we know cases of fusion of nuclei other 

 than in fertilization); and if from this hybrid cell there should 

 then develop a branch by the ordinary process of cell division, 

 then the cells of that branch would all possess protoplasm and 

 chromosomes from both stock and scion, and a true graft hybrid 

 would exist. This alluring possibility has naturally attracted 

 the eager attention of the experimenters, and already they have 

 announced success, though as yet of a somewhat unsatisfying 

 character. And if by good fortune I have ever the privilege of 

 preparing a new edition of this book, I shall probably be able to 

 describe much that is important and interesting in this connec- 

 tion; for this line of experimentation has opened up much more 

 than merely this question of graft hybrids. 



