328 Osborn . — Spongospora subterraneo , ( Wallroth ) Johnson. 
diophora Brassicae , Woronin. It is stated by Johnson to be rampant in the 
West of Ireland ; references to its occurrence in this country have not been 
infrequent during the last few years in the ‘Journal of the Board of Agri- 
culture ’, and I have obtained specimens from more than one locality in the 
neighbourhood of Manchester. 
In its earliest stages, which are visible on young tubers not larger than 
hazel-nuts, the disease is apparent by small slightly raised pimples, and 
a slight discoloration of the surface. When cut open, the infected areas 
appear faintly purplish and extend from approximately the outermost cells 
of the tuber towards the deeper layers. As the organism matures the 
surface of the potato above the diseased portions becomes ruptured. If the 
soil is dry, wound cork is formed, and the extent of the injury is quickly 
limited. In damper soils cork formation being checked, the infected area 
becomes hollowed out, this hollowing being continued as the tuber develops 
until large cavities over an inch in diameter and of considerable depth are 
produced. 
There is not any apparent hypertrophy of the tissues such as is caused 
by Plasmodiophora and Sorosphaera Veronicas } The disease, moreover, 
would seem to be limited to the tubers, though I have occasionally found 
small scabs on the rhizomes as well, but never on the aerial portions of the 
plant. 2 
My own observations as to the transmission of the disease from infected 
‘ seed ’ or soil to sound ‘ seed ’ potatoes have been entirely negative. I have 
planted tubers of ‘ Up to Date ‘Factor’, and ‘Conquest’ in pots of infected 
soil and side by side with infected ‘ seed ’, under varying conditions of 
moisture and temperature; but in no case was I successful in inducing the 
disease. 
It has not been a part of the present investigation to test any remedies 
or chemical checks to the disease. 
Methods. 
Material was fixed in almost every case in the weaker Flemmings 
solution. Acetic alcohol was tried, but this was not successful, owing to 
a shrinkage of the tissues and an apparent hardening of the starch grains 
which interfered with the section-cutting. The material was brought 
through ten per cent, glycerine to absolute alcohol, cleared in chloroform and 
embedded in wax with a melting-point of 54 0 C. Microtome sections were 
cut at thicknesses varying from 2-10 /x (4/x was most frequently used) and 
1 Bloomfield, J. E., and Schwartz, E. J. : Annals of Botany, vol. xxiv, 19T0, p. 35. 
2 Schwartz, E. J. : Annals of Botany, vol. xxiv, 1910, p. 511. Sorosphaera Jnnci is limited 
to the roots of certain species of the Juncaceae, and does not produce hypertrophy of their tissues. 
I am much indebted to Mr. Schwartz for giving me material of S. Veronicae and S. Junci for 
comparison with Spongospora . 
