BRIEFER ARTICLES. 
THE AECIDIUM OF MAIZE RUST. 
THE great economic importance of the corn (maize) crop lends special 
interest to any discovery relating to the habits and development of corn 
parasites. It is partly for this reason, and partly because it illustrates a 
method of observation not yet commonly understood, that the following 
narrative of the discovery of the aecidium of Puccinia Sorghi Schw., the 
common rust of corn, is given here in advance of the season’s culture 
work, of which it forms a part, and which has been undertaken in coopera- 
tion with the Bureau of Plant Industry of the U. S. Department of Agri- 
culture. 
As corn rust is practically coextensive in geographical distribution with 
the cultivation of its host, although rarely so abundant and destructive 
as to attract the attention of the cultivator, and as no aecidium has seemed 
even in the remotest way to have connection with it, the view has gained 
ground that either an aecidium is no longer produced in its life-cycle, or 
that it occurs only in regions where corn was originally wild. In the latter 
case the aecidium might inhabit some host of restricted range, for all gluma- 
ceous rusts with one exception are heteroecious, and the chances, therefore, 
to detect and prove the genetic connection would be few. I have found that 
corn rust continues to produce uredospores until very late in the fall, in 
fact often as long as the corn plants are alive. On October 9, 1901; 1 
tested uredospores taken from plants in the field partly killed by frost, 
and found that they germinated well in drop cultures. It would seem 
possible for the rust in northern regions to be wholly distributed by uredo- 
spores, beginning in spring from a locality sufficiently far southward to 
permit the corn plant to survive the winter. However, all these ruminations 
have taken on a different aspect by the discovery of the aecidium. 
The preliminary observations, which provided the necessary inference 
on which successful cultures were founded, were essentially of the same 
character as those connected with three-fourths of the discoveries in heteroe- — 
cism which I have so far made, and are therefore given in some detail as 4 
typical and suggestive example of the method employed in my work. 
On June second of the present year, while walking through a thick growth 
of weeds bordering a cultivated field, I came upon some plants of Oxalts 
cymosa Small, the common form of yellow wood-sorrel in this region, bear- 
64 [yoLy 
