626 Validity of the Doctrine of Mutation. 



a h\'bricl may have been made on a normal plant, as 

 WiLLE has told me he suspects to be the case in the sup- 

 posed graft hybrid consisting of a pear worked on a 

 white thorn stock. ^ 



The reader who is interested in the direct influence 

 of the stock on the grafted bud is referred to the recent 

 exhaustive studies by L. Daniel. - 



By pruning Cytisus Adanii, Beyerinck obtained very 

 important results on the vegetati\'e segregation of hy- 

 brids. He found that buds which, as a rule, are resting, 

 but which can be made to develop by cutting off the 

 higher branches, tend to produce the characters of C. 

 Laburnum or of C. pur pur ens, so that we have it in our 

 power to multiply the number of such segregations at 

 will. More than one hundred instances were obtained 

 by him on some few trees. Sectorial segregations of 

 buds also occurred, sometimes transforming a longitu- 

 dinal half of a shoot into C. Laburnum, whilst the other 

 half remained C. Ad ami. ^ It is to be expected that the 

 application of this principle to other cases will lead to the 

 discovery of important facts. 



Of the numerous instances of bud-variations de- 

 scribed in the literature of this subject, many are, with- 



p. 237. Also Laurent, loc. cit., p. 16. For a general review of graft 

 hybrids see Fruwtrth. Zitchtimg landwirthsctiaftJichcr Kultnrpflan- 

 ccii, p. 72 ff. 



^ N. WiLLE, Mitfhcihingcn d. hiolog. Gcsellschaft in Chrisfiania, 

 Biol. Centralblatt, 1896, Vol. XVI, No. 3, p. 126. Perhaps this may 

 be Pynis aurictiJaris {P. communis X Sorhiis Aria) or a related hy- 

 brid. See DiPPEL, Handbuch dcr Lauhholzkiinde, III, p. 359. 



^LuciEN Daniel, La variation dans la grcffc cf Vhcrcditc des 

 caractercs acquis, Ann. so. nat. bot., 1899, Vlllth scr., Vol. VIII. 

 pp. 1-226 and Plates I-X, and the subsequent publications of the 

 same author. 



^ M. W. Beyerinck, Kan. Akad. v. Wctensch., Amsterdam, Nov. 

 1900. 



