1878.] BOTANICAL LETTERS. 349 



more vigorous constitutions and generally are more prolific 

 than seedlings from self-fertilised parents. It is also probable 

 that cross-fertilisation would be especially valuable in the 

 case of the potato, as there is reason to believe that the 

 flowers are seldom crossed by our native insects ; and some 

 varieties are absolutely sterile unless fertilised with pollen 

 from a distinct variety. There is some evidence that the good 

 effects from a cross are transmitted for several generations ; 

 it would not, therefore be necessary to cross-fertilise the 

 seedlings in each generation, though this would be desirable, 

 as it is almost certain that a greater number of seeds would 

 thus be obtained. It should be remembered that a cross 

 between plants raised from the tubers of the same plant, 

 though growing on distinct roots, does no more good than a 

 cross between flowers on the 'same individual. Considering 

 the whole subject, it appears to me that it would be a national 

 misfortune if the cross-fertilised seeds in Mr. Torbitt's posses- 

 sion produced by parents which have already shown some 

 power of resisting the disease, are not utilised by the Govern- 

 ment, or some public body, and the process of selection 

 continued during several more generations. 



Should the Agricultural Society undertake the work, Mr. 

 Torbitt's knowledge gained by experience would be especially 

 valuable ; and an outline of the plan is given in his printed 

 letter. It would be necessary that all the tubers produced by 

 each plant should be collected separately, and carefully 

 examined in each succeeding generation. 



It would be advisable that some kind of potato eminently 

 liable to the disease should be planted in considerable numbers 

 near the seedlings so as to infect them. 



Altogether the trial would be one requiring much care and 

 extreme patience, as I know from experience with analogous 

 work, and it may be feared that it would be difficult to find 

 any one who would pursue the experiment with sufficient 

 energy. It seems, therefore, to me highly desirable that 



