U7^ Botanical Society of Edinburgh. 



demic. Although we may not have discovered the causes of epidemic 

 diseases, we know they depend partly on local or individual circum- 

 stances which may be obviated, and which influence some epidemics 

 more than others ; and partly to general influences, commonly sup- 

 posed to be atmospheric, but regarding which we actually know no- 

 thing but their existence. Mr. Goodsir then alluded to the striking 

 general resemblance between the rise and progress of epidemics, and 

 the appearance, non-appearance, and increase of fungi from season 

 to season. Coupling this analogy with the opinion generally gaining 

 ground, that certain epidemics owe their existence to the growth of 

 fungi or analogous beings in the animals aflElicted, Mr. Goodsir con- 

 ceived that we are bound, in our attempts to explain the nature of 

 the potato disease, not to overlook the fungi which exist in the dis- 

 eased tubers. After stating Mr. Berkeley's late researches into the 

 fungoid nature of the disease, Mr. Goodsir observed, that he was still 

 inclined to believe^in the organic nature of the brown matter ; and he 

 founded his belief chiefly on its peculiar form, and on its position in 

 the cells. This view of the nature of the potato disease did not aflford 

 an indication of cure or prevention, for the diseases with the nature 

 of which we are best acquainted are not always those we can most 

 certainly cure. It holds out, however, a hope that the murrain may 

 not recur. The occurrence of fungi as the cause of disease was 

 pointed out in various instances, especially diseases of the skin where 

 mycodermatous fungi are seen, diseases of the mucous membrane, 

 and diseases of the stomach. The occurrence of cellular plants {To- 

 rula cerevisice) during fermentation was also alluded to as corrobora- 

 tive of Mr. Goodsir's views. The paper was illustrated by large 

 drawings of the diseased structure of the potato, of the brown gra- 

 nules, and of Botrytis infestans, «Stc. 



Dr. Greville in making a few observations, commenced by paying 

 a high compliment to the talents of Mr. Goodsir, and the general 

 accuracy of his microscopical researches. " With reference to that 

 gentleman's theory," said Dr. Greville, "I see nothing improbable in 

 the potato murrain being analogous to epidemic diseases in the ani- 

 mal kingdom. In fact the analogies between the two great kingdoms 

 of organized matter are so many and so strong, that he might reason- 

 ably look for much similarity among some of the phaenomena exhi- 

 bited in both, with regard to disease. Like epidemics in the animal 

 world, the one under consideration has appeared almost simultane- 

 ously in various and remote parts of the globe ; a fact which seems 

 to indicate some atmospheric influence. The real cause, as in the 

 case of all epidemics, is involved in the greatest mystery. Possibly 

 a union of conditions may have taken place favourable to the deve- 

 lopment of the fungus which appears to be invariably present. We 

 all know that in the germination of monocotyledonous and dicotyle- 

 donous seeds a union of three conditions is essential, — the presence 

 of air, warmth, and moisture. If any one of these conditions be 

 wanting, the seed will not germinate, but, if otherwise favourably 

 circumstanced, will remain in a dormant state for an indefinite pe- 

 riod. In like manner I think it not improbable that certain con- 



