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The Oxydases of Cytisus Adami. 

 By Frederick Keeble, Sc.D., Professor of Botany, University College, 

 Beading, and E. Frankland Armstrong, Ph.D., D.Sc. 



(Communicated by W. Bateson, F.R.S. Beceived May 29, — Bead June 20, 1912.) 



The graft-hybrid Cytisus Adami — that classic of botanical speculation and 

 research — is one of the wonders of the vegetable world. Every year the 

 trees, which have been propagated vegetatively from the original creation 

 of the French gardener Adam, may be seen to bear blossoms of three 

 kinds, buff, yellow, and purple. The yellow flowers are identical with 

 those of the common laburnum {Cytisus laburnum), the purple resemble 

 those of Cytisus purpureus, and the buff coloured flowers appear to combine 

 the characteristic features of C. laburnum with those of C. purpureus. 



The history of the origin of C. Adami has been told repeatedly (cf. Darwin, 

 1888). There is good ground for believing that it was produced by budding 

 C. purpureus on C. laburnum. The plants raised as a result of the operation 

 were — according to Dai^win's account — distributed originally as C. purpureus, 

 and it was not till later, when they began to exhibit their diversity of flower, 

 that they were described as graft-hybrids. Notwithstanding the attention 

 that has been given to the subject, the nature of the union between the two 

 species remained obscure for many years. 



Becently the brilliant researches of Baur (1909) and Buder (1910) have 

 led the former author to formulate an hypothesis which has the signal merit 

 of presenting a precise and diagrammatic picture of the biological construction 

 of C. Adami. 



On this hypothesis, the graft-hybrid is to be regarded as a periclinal 

 chimera ; that is to say, it is a dual organism composed externally of one 

 species and internally of another. The contribution of C. purpureus to the 

 chimera consists of a superficial single-layered epidermis ; the rest of the 

 body of C. Adami is built up of tissues contributed by C. laburnum. The 

 hypothesis, which is supported by the results of investigations into the 

 comparative anatomy of the component species and the graft-hybrid, and also 

 by analogy with other graft-hybrids, permits of a postulation of the modes 

 of origin of the several kinds of flowers borne by C. Adami. Thus, branches 

 of the graft-hybrid in which the periclinal duality is maintained bear 

 flowers with a purple epidermis and yellow sub-epidermal cells. The com- 

 bination results in a buff colour. Those branches which, for some reason or 

 other as yet unexplained, are produced solely by the sub-epidermal laburnum 



