65 
ON THE LIFE HISTORY AND MORPHOLOGY 
OF UROCYSTIS CEPULAE 
With Plate II. 
By T. Whitehead, A.R.C.S. 
Laboratory of Plant Pathology, University College, Bangor. 
Urocystis Cepulae is the cause of a destructive smut disease 
of onions which has resulted in thousands of acres of land in 
the United States being rendered unsuitable for the growth of 
this crop. The existence of the disease in several localities in 
Great Britain(x) resulting in some years in a total loss of the 
crop has shown the necessity for taking steps to eradicate this 
smut, or at least to restrict it to those places where it now 
occurs. 
The present investigation was undertaken concurrently with 
the laying down of field experiments with a view to opening 
up new lines of attacking the problem of control. It is mainly 
concerned, therefore, with those features of the life-history and 
morphology of the fungus, a knowledge of which would best 
serve the immediate purpose in hand. 
HISTORICAL. 
In 1889 Thaxter(z) published an account of the history of 
the disease up to that date, together with a general description 
of the causal fungus. So far as the writer is aware no further 
attempt has been made to study the life history of Urocystis 
Cepulae though much has been written on suggested measures 
of control. 
It is desirable to give here a short summary of the history 
of the disease since Thaxter’s paper is inaccessible to most 
workers in this country. Indeed the present work was well 
advanced before the writer, through the kindness of Prof. 
Thaxter was able to obtain his paper. Onion Smut has been 
known in Connecticut since 1860. It first attracted attention 
as a serious disease in Massachusetts in 1869-70. About 1876 
the fungus was given its present name by Mr C. C. Frost of 
Brattleborough, Vermont. Previously it was referred to the 
genus Peronospora. A short account by Farlow appeared in 
1876-77 and this was followed in 1889 by Thaxter’s paper 
mentioned above to whom most of our present knowledge of 
the fungus is due. 
Thaxter gives the distribution of the smut as Connecticut, 
Massachusetts, Ohio, Pennsylvania and possibly several other 
M.S. = 
