the 'Potato Disease, dc. 197 



character and reputation. In the case of such new produce, 

 it must be indubitably established that it is from seed — a 

 cardinal point not to be entrusted to any one who is to 

 make money by it. The experiment should, therefore, be 

 undertaken by gentlemen who look for no recompense, and 

 whose sole object is to confer a benefit on their country 

 and their fellow-man. Still, more especially, does it appear 

 to me to fall within the province of this Society to conduct 

 such an experiment : we have a virgin and not ungenerous 

 soil — our climate is most favourable to the plant — we have 

 every means and appliance at command ; and I am very 

 confident that there lacks not amongst us a disposition 

 animated by the highest motives. 



I now produce to the meeting sections of the leaf, and of 

 the tiiher, of the potato affected by disease as it exists in 

 Ireland, and also of the insects to which the mischief is 

 attributed, for examination through my microscope under 

 a high magnifying power. I am sceptical as to the 

 disease originating with the Aj^his ; it seems to me 

 more likely that the insect is the efiect, than the cause. 

 Disease and decay have two concomitants, fungi and insects, 

 one or both. In England the notion is, that this Aj^his (a 

 species well known to the gardener) is brought by the east 

 wind. It is a notorious fact, that winds from this point of 

 the compass are unfavourable to the health of plants. They 

 predispose, therefore, to blight ; and hence the notion that 

 east winds carry the disease. 



When the elm trees in St. James's Park and the neigh- 

 bourhood of London were observed to be dying, about 

 twenty-five years ago, without any other apparent cause than 

 that they were infested with a grub which groped its way 

 under the bark, the Government appointed several scientific 

 gentlemen to investigate the matter. They came to the 

 conclusion that the unhealthy condition of the trees pre- 



