172 Scientific Proceedings, Royal Dnhlin Society. 



suggested what appears to be the line of development followed. In the 

 interpretation of the phenomena in the larger spores of Ceratiomyxa, Jahn 

 and Olive differ fundamentally ; and I may well hesitate in the much 

 more difficult case of Spongospora to interpret the appearances presented. 

 PI. XII., fig. 7, shows some of the stages drawn from preparations under 

 the highest magnifications. 



The possibility that tliere was some justification for the statement made 

 by Berkeley and others, that the spore-balls were attached by a side-stalk, 

 and tliat the fungus was a smut, early disturbed me, and I was quite 

 prepared to find iu the type material of Sorosporium Scabies hyphse in the scab 

 spots. In one section I found cells filled with fungal hyphse as figured 

 (PI. XIV., fig. 4), suggestive of the sclerotium of Ehizoctonia (or Corticium). 

 In some Scotcli material I examined, hyphse were clearly present in the scab 

 areas outside the cellular tissue of the tuber ; and though some could be 

 accounted for as the mycelial hyphse of Ehizoctonia scab, there were others 

 not so explicable (PI. XIV., fig. 5). The hyphse are swollen, septate, and 

 branching ; their contents abundant and granular. In some cases chains or 

 masses of spores may be seen arising from the protoplasmic contents of the 

 hyphse (PI. XIV., fig. 2). Spongy spore-balls, very like those of Spongo- 

 spora, arise ; and ultimately the enclosing walls of the liyphte disappear and 

 leave the balls lying free. The more external balls lose their compactness 

 and break up into single spores or small groups of spores (PI. XIV., fig. 5), 

 so that they form a finer powder tlian Spongospora, whose spore-balls remain 

 intact to the end. The mode of origin of the spores just described is not 

 unlike that met with in the U&tilaginece, so far as they have been studied ; and 

 it thus appears as if (as I wrote in my working notes as long ago as May, 

 1908) there are two kinds of potato scab characterized by powdery spore- 

 balls, the one with a plasmodium — Spongospora subterranea Wallr. — the other 

 a Hyphomycete, possibly one of the Ustilaginacese. 



In 1892, Lagerheim (14) published a short note in the Journal of 

 Mycology, in_ which he stated that the scab observed by Brunehorst was 

 well known to the natives in S. America, though due, they thought, to the 

 gnawing of worms. Lagerheim states that Brunehorst wholly misunderstood 

 and misinterpreted the organism, and that the wart-like tissue is not potato- 

 flesh, but a pseud-parenchyma of fungal hyphse, in which the characteristic 

 spore-balls arise. The hyphse are filled with a colourless protoplasmic 

 substance, which is very often full of vacuoles. This is perhaps, says 

 Lagerheim, what Brunehorst mistook for plasmodia. In the warts, containing 

 mature spore-balls, the hyphse are usually empty, and the spore-balls are not 

 free, but fastened to the surrounding hyphse of tlie pseud-parenchyma. 



