817 



myriads at particular times, and it could not be doubted but that the 

 state of the atmosphere had some direct influence in producing their 

 extraordinary development on such occasions. 



Dr. Ayres said it had been ascertained that there was a deficiency 

 in the development of starch granules in the diseased potatoes to the 

 extent, he believed, of ten per cent, compared with the quantity usu- 

 ally in healthy tubers. There must, therefore, be a greater propor- 

 tion of fluid present ia the root, and a consequent defect of vitality, 

 which would render the plant more liable to the attacks both of 

 fungi and of animals. It was remarkable that all the varieties of 

 fungi found on the diseased potatoes — some dozen he believed in 

 number — were those usually seen on decaying vegetable matter, 

 whereas in the case of the smut in wheat, where another kind of fun- 

 gus appeared, the stem and leaves of the plant remained perfectly 

 healthy, though the smut invariably made its appearance if the spo- 

 rules had been sown with the wheat in the ground. 



Mr. Hassall said he could not agree in Dr. Ayres' remarks. If 

 two apples growing on the same tree were perforated, and the sporules 

 of the fungi applied to one, it would be found that the apple so im- 

 pregnated would become diseased, while the other continued to 

 grow. 



Dr. Ayres said it was clear that in wounding the apples in the first 

 instance the vitality of the cellular tissue was impaired, and the fungi 

 were then able to act upon it, which was the very point for which he 

 contended. 



Mr. Ward said if the leaf of any plant were bruised, so as to in- 

 jure its vitality, fungi would make their appearance upon it as a na- 

 tural consequence. 



Dr. Ayres said there could be no doubt but that fungi were very 

 powerful agents in the economy of nature. For instance, it was now 

 known that the phenomena of fermentation were produced by fungi, 

 and that their influence had the effect in that case of dividing the 

 sugar into alcohol and carbonic acid. 



The Chairman, in closing the discussion, said there was at all 

 events one point on which they were unanimously agreed, and that 

 was, that the real cause of the potato-disease had not yet been clearly 

 ascertained, or at all events that the Aphis rapac, or as Mr. Smee 

 termed it, the Aphis vastator, had nothing to do with it. 



The subject was then adjourned to the next meeting, on the 7th of 

 May, and the proceedings terminated. — Evening Chronicle, April 12. 



