108 

 NOTES ON A GRAFT-HYBRID. 



(By L. Rodway, Government Botanist.) 



Plate X. 



(Read August 9, 1915. # 



Issued separately 31st December, 1915.) 



Recently Mr. Osborne, the fruit expert in the Agricul- 

 tural Department, handed me an apple of which one-half 

 was typical Roman Beauty and the other as surely Senator. 

 There was no blending ; the division was longitudinal 

 through the median plane and as clearly defined as it was 

 possible to be. 



The apple was grown in the orchard of Mr. Bourne, 

 Premayclena, South-East Tasmania. 



The following note is sent with it from Mr. Ward, assist- 

 ant fruJt instructor: — 



"The apple was picked from a Roman Beauty tree 

 winch had been grafted on a Senator stock. The 

 tree is young, as far as I know seven or eight 

 years old. This was the only apple of its kind 

 on the tree." 

 Judging from its history and appearance there seems 

 little escape from the conclusion that this is a genuine case 

 of graft hybridism. Reversion would not have given us a 

 fruit with such a well-marked distinction of character in 

 the two halves. Cross-fertilisation has not yet demonstrat- 

 ed more than at most a slight general influence. The chance 

 of mutation producing such a sport, bearing half the char- 

 acter of the stock and half of the scion, is unthinkable. 

 Till some other reasonable explanation is forthcoming we 

 must fall back on the belief that the Senator stuck is re- 

 sponsible for the presence of the Senator half-fruit. This 

 belief is not new, but its present advance is justified from 

 its unmistakeable authenticity. A considerable difficulty 

 arises when we try to account for the phenomenon. One 

 apple alone was influenced. In other recorded cases it is 

 always a case of partial, not general, influence. Even in 

 experiments with potato tubers the characters are not 

 blended. This points to a vitalistic, not nutritional, cause. 

 If vitalistic, it must be due to a migrating nucleus or an 

 influence transmitted through protoplasmic filaments con- 

 necting stock and scion. If the protoplasts of stock and 

 scion become continuous through such filaments we would 

 expect an) influence transmitted to be general, and not as 



