1524 The Trees of Great Britain and Ireland 



which contained one or two apparently good seeds. Some of these germinated ; and 

 he raised two trees, one of which resembled the parent, but the other was remarkably 

 dwarf in habit with small leaves. 



This hybrid, which is usually sold as L. Watereri or Z. Parksii, is very 

 ornamental, occasionally bearing racemes 16 or 18 in. long, and is said to be very 

 rapid in growth.^ 



II. Laburnum Adami, Kirchner, Arb. Muse. 397 (1864). 



Cytisus Adami, Poiteau, in Ann. Soc. Hort. Paris, vii. 501 (1830), and in Loudon, Gard. Mag. xvii. 



59 (1841). 

 Cytisus Laburnum, Linnaeus, var. coccineum, Lindley, in Bot. Reg. xxxiii. t. 1965 (1837). 

 Cytisus Laburnum, Linnseus, vax. purpurascens, Loudon, Arb. et Frut. Brit. ii. 590 (1838). 



This remarkable hybrid, between Laburnum vulgare and Cytisus purpureus, 

 Scopoli, has normally glabrous branchlets, petioles, and leaves, with leaflets smaller 

 than those of L. vulgare ; and bears dingy red small flowers, in short pendulous 

 racemes, which never set seed. It is usually reproduced by grafting on the common 

 Laburnum, and is remarkable in often producing stray branches which revert back 

 to one or both of the parents. A single tree is thus often seen bearing three kinds 

 of foliage and flowers : {a) the hybrid foliage and flowers ; {b) branches with the 

 yellow flowers and leaves of L. vulgare ; and (c) branches with the leaves and small 

 purple flowers of Cytisus purpuretts? The yellow flowers produce pods which yield 

 fertile seed, from which Darwin ^ raised seedlings resembling in most respects the 

 common Laburnum. The branches with purple flowers are said by Darwin to be not 

 quite the same as those of Cytisus purpureus, and are not perfectly fertile ; but he raised 

 seedlings from their seed which differed in no respect from pure Cytisus purpureus. 



This hybrid is said to have originated in 1825 in the nursery of M. Adam at 

 Vitry, near Paris. He inserted on a stock of L. vulgare a shield of the bark of 

 Cytisus purpureus, which produced in the following year several shoots, one of which 

 was more vigorous and had larger leaves than the others. This shoot was pro- 

 pagated, and as soon as it bore the peculiar flowers intermediate between the two 

 species, was recognised as a hybrid which had been produced by grafting. This 

 account has been disputed by some botanists ; and De Vries,* who has made a study 

 of the plant, states that Camuzet, a contemporary of M. Adam, maintained that he 

 had seen the tree from which the latter had taken his graft, and that it was not 

 Cytisus purpureus, but L. Adami itself, so that the latter must have originated 

 earlier and been an ordinary chance hybrid from seed. Camuzet's statement seems 

 very improbable; and against this view may be stated the fact that Reisseck, 

 Caspary, and Darwin tried in vain to cross the flowers of C. purpureus with 

 those of L. vulgare. 



' Cf. Harrison Weir, in Gard. Chron. xxvi. 83 (1899). 



2 Mixed flowers also occur. Braun, Rejuvenescence (Ray Soc), 317, plate v. (1853), gives an instance of a raceme 

 which bore 21 flowers of Z. Adami, 3 flowers of Z. vulgare, and 8 mixed flowers. In the latter, half of the corolla was 

 reddish Uke L. Adami, the other half yellow like L. vulgare ; similarly, half of the calyx was reddish brown and glabrous, as 

 in L. Adami, the other half green and pubescent, as in L. vulgare. 



3 Variation of Animals and Plants, i. r4J4 (1890). 



4 Mutation Theory, ii. 622, figs. 139, 140 (1911). Cf also Bateson, in Nature, Ixxxviii. 37 (1912). 



