A. H. Lees 21 



with the Seabrook's Black graphs since they have a thickness at the base 

 of 9| mm. for the Chelmsford shoot and 9 mm. for the Long Ashton 

 shoot. The influence of climate is here the same in all respects as in the 

 Seabrook graph. The number of internodes however is less, being twenty- 

 one and seventeen, though the length of the shoot is greater. The inter- 

 nodes are therefore, as can also be seen from a superficial glance, longer. 

 Incidentally it may be remarked that Seabrook's Black is a better type 

 for production of fruit, in that, in a given length of shoot, there are more 

 lateral, that is fruit, buds than in Boskoop Giant. Comparing Seabrook's 

 Black and Boskoop Giant under Chelmsford conditions the great con- 

 centration of internodes in the former at the end of the graph is in marked 

 contrast to the corresponding part of the graph for the latter. It indicates 

 an early check to growth, an indication which is borne out by the numbers 

 of scale scars in the last nine laterals. These in the case of Seabrook's 

 total eighteen while for Boskoop they are twenty-three. One may assume 

 therefore that under the same climatic conditions Seabrook's receives a 

 more decided check to growth than Boskoop. 



If, as has been already assumed, the resistance of Seabrook's Black 

 to Big Bud at Chelmsford is due to the fact that mites kill the bud 

 growing points instead of forcing them into hypertrophied growth it 

 should be possible to show that the conditions at Chelmsford are such 

 as to bring this about more readily than at Long Ashton, where big buds 

 are formed extensively on this variety. It has been shown above that 

 the conditions at Chelmsford cause an early and marked summer check 

 to terminal and lateral growth and therefore it is likely that mite 

 attacked buds will have their sap supply very much curtailed at the 

 time of this summer check. There will therefore be more tendency for 

 these growing points to be killed by the mite attack than in the Long 

 Ashton climate where growth continues longer. These facts also explain 

 why some big buds are formed at Chelmsford and why they are practi- 

 cally always situated low down on the shoot. For it is just these buds 

 that have been growing the longest and must have been, from their 

 position, earliest attacked. A big bud therefore is formed from a growing 

 point that has been attacked early and has had abundant and long con- 

 tinued sap supply while a killed bud is formed from a growing point that 

 has been attacked late in the season and has a poor and brief supply of 

 sap. 



These considerations explain why some big buds are formed on Sea- 

 brook's and also why they do not increase in number. Probably it will 

 be found that in wet years they do increase and in dry years disappear. 



