ii8 The Irish Naturalist. May, 



DUBLIN MICROSCOPICAL CLUB. 



March io.— Tbe Club met at Leiiister House. 



Dr. G. H. Pethybridgk (Presideut) exhibited the so-called '-'spore- 

 balls" oi Spongospora siibterranea (Wallr.) de Lagerh. This organism is 

 found associated with oue of the forms of scab in potato tubers and is 

 generally regarded as the cause of it. It was first described by Wallroth 

 in 1842, who gave it the name of £"/ji-/<^^? subterranea. Later in the same 

 year it was seen and figured by Martins, who, considering it to belong 

 to the genus Protomyces, named it Protomyces iuberum solani. Berkeley 

 figured and desciibed it again, in 1S46, under the name of Tubiircitiia 

 scabies. Ten years later it was described and the "spore-balls" 

 excellently figured by Von Mercklin, who, however, did not consider it 

 to be a fungus, but thought, rather that the spore-balls were degenera- 

 tion products of the cells of the potato tuber, and, consequently, he gave it 

 no name. At this earh" period not very much attention was paid to the 

 parasitic nature of the organism or to the damage which it caused. 

 For many years it appears to have been lost sight of, until Brunchorst, 

 in 1887, without being aware of the previous accounts of the organism, 

 found it causing considerable damage to potato tubers in Norway and 

 described it as a new genus and species under the name of Spongospora 

 Solum'. Fischer de Waldheim had, ten years previously, transferred it to 

 a position among the family of ''smuts'' and re-named it Sorosporiitvi 

 scabies, but Brunchorst considered it as probabl}' belonging to the class 

 of Myxomycetes. It is highly interesting to notice that de Lagerheim 

 reports it, in 1891, as being quite common in the neighbourhood of 

 Quito, the probable home of the potato plant itself. This observer dis- 

 agrees with Brunchorst as to the nature of the organism, and considers 

 that whatever it may be it is certainly not a m3'xomycete. It was de 

 Lagerheim who first suggested that the correct specific name for the 

 organism as siiblerranea (Wallr.) It was first recorded from Ireland by 

 Johnson, about 1904, and has since been found to be quite common here- 

 especially in the west. Johnsons studies lead him to accept Brun- 

 chorst's view of the organism as being a myxomycete, and, without 

 entering deeply into the question of nomenclature, he apparently 

 accepts the name given to it by Brunchorst, at least provisionally. Not 

 so, however, Massee who, being apparently in ignorance of de Lager- 

 lieim's paper and of Wallroth's original description, has, unfortunately, 

 and quite unnecessarily, added yet a fresh combination of names (^Spon- 

 gospora scabies) to this already much named parasite. 



The organism in mild cases forms a " scab " on the surface of the 

 tuber, which has been called, perhaps not very happily, '"corky scab," 

 and which, with the naked eye, is not very easily distinguished from the 

 ordinary or brown scab. It is true that sometimes the spore balls of 

 the fungus are plentiful enough to form a rusty-coloured, granular mass 

 on the scab, plainly visible with a pocket lens, but this is frequentl}- not 

 the case, and the microscope is necessary in order to distinguish with 

 certainty between the two forms of scab. The exhibit also included a 



