MINUTE STRUCTURE OF PLANT HYBRIDS. 259 



IV. Cytisus Adaml 



Before attempting to generalise on the facts gathered from investigation of sexual 

 or seed hybrids, we may first examine minutely a plant which has excited universal 

 attention and interest since its first production in 1825. I refer to Cytisus Adami, now 

 regarded by most as a graft hybrid. Darwin * summed up the generally received ideas 

 regarding it, and added additional valuable observations. A list of leading papers on 

 the subject is appended, which may guide those who wish to trace the literature of it.t It 

 may suffice here to say that M. Adam, a nurseryman near Paris, budded, according to his 

 own account, a shield of the small tufted species C. purpureus on the common laburnum 

 (C. Laburnum), hoping only thereby to get a stronger and more free-flowering variety 

 of the former. The bud seemed for the time to die back, but from the region of its 

 insertion a strong shoot developed later, which he considered to be the desired bud sport 

 of C. purpureus. As such he sold it, and we may judge of the surprise excited when 

 it was found a few years later that this assumed an arborescent habit, and broke out 

 into yellow and purple portions similar to branches of the parents, as also into strong 

 twigs, bearing flowers exactly intermediate in form and colour. 



Some have attempted to assert that we have to deal here with an ordinary seminal 

 hybrid, but not only have we the unvarnished account given by its producer, the striking 

 mixture and at the same time sharp distinctness of the three growths which make up the 

 composite organism and are simultaneously produced on it, leave little doubt in my 

 mind of its graft-hybrid origin. I know of no seminal hybrid which imitates it, though 

 one or two approach it, as, for example, Noble's Clematis and Berberis Neuberti.\ I 

 wish further to show that the microscopic characters agree with such a conclusion. 



No account of its histology had appeared when I published my preliminary note in 

 the Gardeners' Clironicle ; but shortly after Marzell Branza referred § to it in a few 

 sentences thus : — 



" Medicago falcata-sativa. — This plant presents in its different parts (trunk, stalk, 

 floral axis, petiole), and in all the tissues of its organs a kind of medium between the 

 same parts of the two parents. Thus, for example, the stem by the disposition of the 

 bark, of the liber, of the wood, of the pith, establishes the transition between the stem of 

 Medicago falcata and that of M. sativa. It is the same in the hybrids Cytisus Adami 

 and Sorbus hybrida." 



* Animals and Plants under Domestication, 2nd edit., 1890, vol. . pp. 413-417. 



t Annates de la Soc. de I'Hort. de Paris, torn, vii., 1830, p. 93; Loudon's Gard. Mag., vol. vi., 1831, p. 335; viii., 1832, 

 pp. 473-474 ; The Phytologist, vol. i. pp. 652, 908 ; Gard. Chron., 1841, pp. 265, 325, 336 ; 1842, p. 397 ; 1857, pp. 382, 

 400, 454 ; 1864, p. 244 ; 1865, p. 509 ; 1866, pp. 565, 733 ; 1868, p. 575 ; 1870, pp. 767, 831 ; 1884, pp. 772, 810, 811 ; 

 Bratjn, "Rejuvenescence," Ray Soc. Bot. Mem., 1853; Bot. Zeitung, 1873; Focke, Pflanzen-Mischlinge, pp. 519-522; 

 Darwin, Animals and Plants under Domestication, 2nd edit., 1890, vol. i., pp. 413-417 ; Morren, E., Belgique Horticole, 

 vol. xxi., 1871 ; Caspary, Bullet, du Congres Internal de Botanique, Amsterdam, 1865, p. 72 ; Masters, " Grafting, its 

 Consequences and Effects," Popular Science Review, April, 1871 ; Macfarlane, Gard. Chron., July 26, 1890. 



\ Masters, Gard. Chron., " Bud Variations," 1891 ; Focke, Pjlanzen-Mischlinge, p. 21. 



§ Comptes Rendus, August 1890. 



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