330 GENERAL PLANT PATHOLOGY 



constituting Cylisus Adami. It was found, that on flowering, this 

 form had dingy red flowers. Winkler believes that graft hybrids and 

 chimaeras are the result of the process by which cells of two distinct 

 kinds or species are united vegetatively instead of by sexual methods, 

 and that this serves as the point of departure for an organism which in 

 a single growth shows bound together the peculiarities of both species. 

 Hence, a graft hybrid is a complex chimsera. Baur thinks that the 

 union between CraUegus and Mespilus {CratagomespUus) is a periclinal 

 chimaera, and refers this and the graft hybrid to the development of a 

 mixed vegetation point, where the periclinal chimaera originates in 

 the development of an apical region with a periclinal arrangement 

 of cells. ^ 



Branches of shrubs and trees originate as mutants with a different 

 combination of characters than the rest of the shrub, or trees. Such 

 mutants probably arise in the change of some single cell. The shoot 

 which arises from tissue formed by mutating cells develops into 

 something new which is called a bud variation, or sport variety. If 

 th.e shoot arises from the mutating cells alone, then the resulting 

 shoot wiU consist only of the new cells and the sport can be propagated 

 true without any reversion. If the tissue which gives rise to the shoot 

 combines both old and new cells, then there arises a mixed branch, 

 which is known as a "sectorial chimaera." Citrus treess how such 

 "sectorial chimaeras" not infrequently when a Valencia orange tree 

 bears typical Valencia oranges and a small rough and worthless muta- 

 tion. A twig here and there produces oranges in which certain sectors 

 of the fruits show mutant tissue,^ forming what may be called mixed 

 oranges. These have probably arisen because the mutant tissue is 

 scattered or mixed with the tissue of the original form thus constituting 

 a "hyper chimaera." 



"Mutations often occur in the cells which begin the formation of 

 the minute ovaries in the blossom buds. As the ovary grows in size, 

 the mutation appears as a sector of the fruit which differs in color, 

 ripening season, or thickness of skin from the rest of the fruit. Such 

 curious fruits have been called spontaneous chimaeras" (Coit). 



•Winkler, H.: Ueber Pfropfbastarde und Pflanzliche Chimaren. Ber. 

 Deutsch. Bot. GescUsch., 25: 568-576, 1907; Baur, E.: Pfropfbastarde, Periklinal 

 chimaren und Hyperchimaren, Do., 27: 603-605, 1909. 



^ Coit, J. Euot: Citrus Fruits, 1915: 121-122. 



