Botanical Society of Edinburgh, 379 



state, as if they had been filled with fluid by endosmose, and the com- 

 partments of the cellular tissue had thus become so entirely detached 

 from each other, as to have assumed a complete round form, instead 

 of their characteristic hexagonal shape. It appeared to him to re- 

 semble what might be expected from the maceration of the textures 

 in water, and it was a possible 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 ap- 

 peared 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 atmosphere, was there anything in the state of the at- 

 mosphere to account for it in one part of the globe and not in another ? 

 He had been devoting attention to the meteorological branch of the 

 inquiry, and he thought that he had made a discovery, which would 

 explain the appearance 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 So- 

 ciety, could take part in the proceedings ; he would therefore indi- 

 cate generally the results. Mr. Milne then described some peculia- 

 rities of the weather in England and Scotland during the summer 

 and autumn of last year, as shown by meteorological returns which 

 he had obtained from a number 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 the 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 thermometric 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, 

 or some cause which did not take effect till the tubers were fully 

 developed. 



2. " A Synopsis of the British Species of the genus Rttbiis," by 

 Charles C. Babington, M.A., F.L.S. &c. (This paper is in the course 

 of publication in these Annals.) 



