6 ARTHUR: PROBLEMS IN THE StTuDY OF PLANT RusTs 
into the life-cycle of the rusts. He brought to their study more 
rigid methods of observation than his predecessors, and above all 
he first used culture methods, which have since become the crucial 
test of all uredineous species, and the key to the complex cycle of 
their development. It was in January, 1865, that Professor Anton 
DeBary, of Freiburg, laid before the Berlin Academy a paper 
dealing especially with the development of Puccinia graminis and 
its connection with Aecidium Berberiais. It was the opening of a 
new era in the study of plant rusts. Botanists had already become 
somewhat familiar with the succession of aecidial, uredo and 
teleutosporic forms among the rusts, but DeBary took up the most 
difficult, complex, and enigmatical of all the rust species, which 
at the present day even is very far from being fully understood ; 
I refer to the black rust of grains, especially of wheat, which 
economically as well as scientifically is no mean problem, as it 
causes a loss in this country alone of some millions of dollars a 
year. He studied the germination of the spores from the wheat 
plant, and acting upon a suggestion derived from the practical 
farmer sowed the teleutospores upon barberry leaves, and raised 
cluster-cups. For more than a century the close observer of farm 
crops had strenuously maintained that barberry bushes near wheat 
fields increased the amount of grain rust, and the botanist had 
scornfully laughed and asserted that no known fact in nature war- 
ranted such an absurd idea; but DeBary vindicated the farmer. 
The following year DeBary announced that oat rust bears its 
aecidia. upon buckthorn leaves, and that rye rust has its aecidia 
upon alkanet, an Old World weed. The same year Oersted, a 
Danish botanist, published the results obtained by the DeBary 
culture method, showing that the rust of cedar trees is connected 
with the cluster-cups on leaves of pear trees. 
Thus was the new doctrine of heteroecism established: the 
existence at different periods of growth of unlike forms upon 
totally unlike host plants. Its acceptance, however, was slow, 
and the culturists were few. During the seventies and eighties 
the attitude of most botanists was far from cordial. A few ac- 
cepted the doctrine, but it exerted little influence upon the course 
of development of the general subject of uredinology. 
It was, however, during this period that cultures were made by 
noite ty es 
