246 APPENDIX. [No. XV.B. 



the young shoots are blighted, become withered and dried up, crumbling 

 under the slightest pressure : from these trees the creature has flown into 

 various other plants in their neighbourhood. On the turnip, it may be 

 found on the under-surface of the leaf; it has also made its appearance 

 on the potato plant. The first vastator which I observed on the potato in 

 open situations was found on May 24th, since which time I have found it 

 sparingly in every district round London ; at present they are scarce. In 

 answer to an attempt which has made to show that my observations last 

 year were made upon a small tract of ground, I beg to state that the 

 plants were narrowly watched over an extent of country of not less than 

 400 or 500 square miles, and I obtained insects and specimens from 

 various other parts of the country ; my observations during the last week 

 have not been less extensive. "With respect to this crop, the leaves look 

 exceedingly well, although below ground ; in most situations there is 

 extensive decay in the stalks. Several practical men think but little of 

 this decay, but there appears to me no question of its importance. I have 

 noticed little tubers, hardly so big as a pea, to be separated from the 

 parent stalk by the destruction of the stem. In a former report I 

 mentioned that I had Russian tubers perfectly healthy, though much 

 damaged in their transit by salt water. It is very curious that the 

 greater number which were left have become thoroughly rotten, and 

 many which grew have since exhibited the gangrene, at the underground 

 stems. 



At the present time there is not much to be done. With regard to 

 the renewed attack on the potato plant, I should be inclined to be passive, 

 because any attempt to remove the very few aphides which now exist 

 might injure the plants rather than benefit them : the gardener should 

 destroy the insect by any of the methods he already well knows. 



Besides the vastator, there are still other aphides committing their 

 ravages. On the melon and cucumber may be found thousands of a very 

 minute aphis, feeding upon the under-surface of their leaves ; and, on the 

 rue, there are no less than three different species now to be found. 



Under all circumstances, the present extremely hot weather is favour- 

 able to the development of aphides ; and, therefore, I am afraid we may 

 expect a repetition this year of the injury to the potato plant. 



INFLUENCE OF THE VASTATOR ON DIFFERENT KINDS OF POTATOES. 

 To the Editor of the 'Farmers' Journal.' 



SIB, In my treatise on the Potato Plant I have developed the im- 

 portant law of the unequal action of the vastator on different kinds of 

 potatoes. It is singular that so manifest a range of facts should pre- 

 viously have escaped attention; but now let us lose no time to take 

 advantage of its application. 



The unequal action of the vastator on different kinds of potato plants 

 must be attributed to two causes their unequal exposure to the destruc- 

 tive influence of the vastator, and to the unequal capacity of different 

 kinds to resist its deleterious agency. 



