Mil. BERKELEY ON THE POTATO MURRAIN. 29 



of greening, I found evident traces of mycelium within them. 

 Little attention was paid to the circumstance at the time, though 

 I made a sketcli of the appearance, whicli will be found amongst 

 the figures. The potato was then exposed to the light and sun 

 in the window of my study, the weather being dry, when, to my 

 great surprise, in a few days it exhibited the spots peculiar to the 

 disease, and was, in a few days more, completely decayed. lam 

 not at all certain that the mycelium was connected with the 

 spots, but the circumstance seems worth recording. 



The disease, if it be due to any specific cause, which I think 

 is clear, however obscure that cause may be, can scarcely be ex- 

 pected, after having had so extensive a range, to subside all at 

 once. The same atmospheric conditions which have favoured 

 its progress are not likely to occur again ; but still I fear that it 

 will be felt directly or indirectly for some time, as in the human 

 frame the general prevalence of a particular disease modifies 

 other diseases for many successive seasons. Such, I am assured 

 by one of the most intelligent practitioners in England, and 

 than whom no one has paid more attention to the particular dis- 

 ease or been more successful in its treatment, has been the effect of 

 cholera in a large town where it was extremely prevalent. Dis- 

 eases appear under a new type and require a different treatment. 

 A diseased stock can scarcely be expected to produce a perfectly 

 healthy offspring. 



On the supposition that it springs from some contagious matter, 

 we can form no probable conjecture, except by mere analogy ; 

 but if it arises from a parasitic fungus, it may be hoped from our 

 experience of other productions belonging to the same tribe, tliat 

 succeeding conditions of the atmosphere may be more or less un- 

 favourable to its development, for it is most certain tliat the 

 germs of cryptogamic plants may be present in tissues and yet 

 remain more or less inert, unless peculiar circumstances should 

 concur — exactly as the seeds of phaenogamous plants may lie 

 dormant in the earth for centuries. 



The Irish Commissioners have wisely taken a wide view 

 of the subject in their reports, and in a case of such difficulty it 

 is seldom safe to trust entirely to one's own particular views. 

 The safest and tiie best plan on every account is to keep our 

 minds in a condition to meet the subject, should it unhappily 

 obtrude itself again upon the attention of the public, without 

 prejudice, and we shall then have some prospect of discovering 

 the proper remedies. 



I come now to the more purely botanical part of the question, 

 namely, the description of the parasite which has been so con- 

 stant an attendant on the disease. And here, as if no part of 

 the matter were to be free from debate, a little difficulty presents 



