THE USE OF SHOOTS FOB PEOPAGATING 195 



two individuals, they retain for many years a sinuous course 

 which retards the passage of substances. 



The changes which take place by grafting cause for a number 

 of years a retardation of the transport of food material. 



But several examples may be mentioned of apparent changes 

 brought about by grafting, one of the most remarkable of 

 which is the transmission of a white-leaved condition (cdbicatio) 

 from the scion upon the stock, and also vice versd {Passiflora, 

 Jasminum, Abutilon)} 



It is less common to find that the occurrence of red cell 

 sap in the leaves of the scion has extended to the wild stock. 

 This phenomenon has, however, been noticed in the case of the 

 copper-beech and the red-leaved hazel. The statements as to 

 any effect produced on the flower of the wild stock are very 

 few. A white flowering Jessamine upon which a yellow 

 flowering variety was grafted is said to have occasionally 

 produced yellow flowers. 



But it is very well known that certain stocks have a very 

 pronounced efiect upon the habit of growth of the scion. 

 Apples grafted on Paradise stock or dwarf stock (Pirus prcecox) 

 remain of short stature and often produce flowers in the year 

 following the grafting. Grafted on the Doucin the varieties 



^ This occurrence may perhaps, however, be attributed to mechanical in- 

 fluence. The appearance of white patches or of entire white leaves depends 

 upon the fact that in several portions of the tissues the cell contents appear 

 poor ; no chlorophyll grains are developed, and the protoplasm appears as a 

 colourless flocculent mass. The cells have, therefore, received too little plastic 

 material during their formation, and have not been able to increase the 

 amount they had received. But it is possible in some plants which have a 

 tendency to white foliage to induce the formation of certain white-leaved 

 shoots by a continued pinching back of the young shoots. This may be 

 explained by the assumption that these shoots are induced to develop before 

 they have sufficient plastic matter, and had to develop very rapidly. Now, 

 grafting acts like pinching, and stimulates the lateral buds to growth before 

 they have sufficient food material. The leaves expand, and in the strong 

 illumination soon become old, and cannot produce new food material for 

 the impoverished cells, which therefore remain without chlorophyll. This 

 character would not be transmitted, but would be brought about by the re- 

 moval of the apex of the shoot in the operation of grafting. This also would 

 serve to explain why the appearance of white-leaved shoots does not always 

 take place close to the graft, but often at some distance from the latter, 

 while green-leaved shoots are found close to the point of union. 



