473 



have assumed a complete round form, instead of their characteristic 

 hexagonal shape. It appeared to him to resemble what might be ex- 

 pected from the maceration of the textures in water, and it was a pos- 

 sible supposition that this might be the first stage of the disease, and 

 that the change thus effected in the tuber formed a nidus fitted for the 

 development and growth of the fungus already existing in the aerial 

 parts of the plant. 



Mr. Milne being invited by the President to give his opinion, stated 

 the gratification with which he had listened to the statements made 

 by Mr. Goodsir and other speakers. Nothing could be more distinct 

 than the description given of the nature of the fungus which appeared 

 to accompany the disease, and the parts of the potato affected by it. 

 The discussion, however, had been confined entirely to a description 

 of the fungus, and to speculations on its probable effect in altering 

 the condition of the potato. No one had, as yet, offered any opinion 

 as to the circumstances which led to the production of the fungus. 

 If it arose from seeds dormant in the potato, what was it which had 

 caused them to germinate .? If it arose from seed or matter in the at- 

 mosphere, was there anything in the state of the atmosphere to account 

 for it in one part of the globe and not another ? He had been devot- 

 ing attention to the meteorological branch of the inquiry, and he 

 thought that he had made a discovery which would explain the ap- 

 pearance of the disease in some places and not in others. But he had 

 not come prepared to enter into particulars, not supposing that any 

 persons, unless they were members of this Society, could take part 

 iti the proceedings; he would therefore indicate generally the results. 

 Mr. Milne then described some peculiarities of the weather in Eng- 

 land and Scotland during the summer and autumn of last year, as 

 shown by meteorological returns which he had obtained from a num- 

 ber of places, both in those districts where the disease prevailed, and 

 in those from which it had been absent. He mentioned that the 

 maximum summer heat had occurred in England and southern parts 

 of Scotland in June, whereas in the northern parts of Scotland, where 

 the potato-disease had not appeared, the maximum heat had occurred 

 in August, as usual. He alluded also to repeated and sudden ther- 

 mometric changes which had occurred in the south of England. 



Mr. Brand and Mr. Girdwood remarked, that potatoes in the early 

 part of the season were not affected, and that where the stems and 

 leaves had been cut away early, the disease had not appeared in the 

 tubers left in the ground. These facts seem to indicate some atmo- 

 spheric influences which had come into operation late in the season, 



