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XVI. 



FURTHER OBSERVATIONS ON POWDERYi POTATO-SCAB, 

 SPONGOSPOBA SUBTEBllANEA (Wallr.). 



By T. JOHNSON, D.Sc, F.L.S., 

 Professor of Botany in the Royal College of Science, Dublin. 



(Plates XII.-XIV.) 



[Read Apeil 20. Ordered for PubUeation May 11. Published July 24, 1909.] 



In February, 1908, I gave an account of a scab(l) of the potato-tuber which 

 I had found to be very prevalent in the west of Ireland. I have had tubers 

 similarly diseased from other parts of Ireland, as well as from England and 

 Scotland. The scab is due to a slime-fungus, described in part and named by 

 Brunchorst (2) in 1886 as Spongospora Solani. In the paper mentioned, and 

 an earlier one, (3j I sought to fill in certain gaps in the life-history of the 

 fungus, more especially in reference to its relation to the host, its 

 Plasmodium, the structure and germination of the spores. I sent samples 

 of scabby tubers to Kew for the Museum, and, in acknowledging them, 

 Colonel Prain, the Director of the Grardens, replied : — 



" Kew, Febniarij 17th, 1908. 



" Very many thanks for the specimen of Spongospora Solani of 

 Brunchorst. We are inclined to think that it is the same fungus as 

 was described in the first instance by Berkeley as Tuhurcinia Scabies, and 

 afterwards transferred to Sorosporium as S. Scabies by Fischer de Waldheim ; 

 Fischer's name has been taken up by Saccardo and by Massee. I am 

 sending you a fragment of the type which is in this Herbarium. As you 

 have been at work on the Spongos^jora, you will be able to say straight away 

 whether the two are the same or are different." 



Massee had already (Gardeners' Chronicle) stated that the new scab was 

 nothing but the scab described by Berkeley fifty years ago, and in 1904, the 

 year in which I first saw and described the scab, he gave in the Journal of 

 the Royal Horticultural Soctety (4) a short account of the scab as the smut 



' "Woimd-cork is such a frequent and marked feature of ordinary scab that I prefer the term 

 "powdery " to " corky" scab, the name I suggested in my earlier paper. 



SCEENT. PROO. E.D.S., VOL. Xn., NO, X\X 2e 



