Ee eens wen ee a 
1898 | RESEARCH INTO GRAIN RUST 35 
crop of spores maturing during late autumn is able to germinate 
the following spring. 
All that I have now set forth—(1) the multiplicity of fungous . 
forms producing the rust disease, (2), the obstinacy of some 
uredo- and ecidiospores in germination, (3) the great impor- 
tance of the matter of distance, and (4) the conditional and 
short-lived germinating power of the teleutospores—cannot 
well be brought into agreement with the view which has been 
held, and is yet generally prevalent, with regard to the outbreak 
and propagation of grain rust, and we may perhaps say of para- 
sitic plant diseases in general, viz., that it is the continual acces- 
sion of new infective material and the continual formation of 
new centers of infection which cause the outbreak and the 
intensity of the disease. The five theses set forth above give 
each in its degree a hard wrench to the cornér stone upon 
which the whole doctrine of grain rust has been resting for a 
long time. 
It may be biked whether this overthrow of prevailing opin- 
ions is the only or principal result of the investigations. Does 
it not present some more positive result, some new starting-point 
upon which a new doctrine may be founded, and from which new 
work may begin? I am obliged to be brief at this time, and to 
give merely a short and summary review of my results, referring 
for details to the special works already published or soon to be 
published. 
I shall first call attention to two observations that were easily 
made, but no less remarkable for that reason. Each of them 
gave cause to suspect a source of rust quite different from that 
which we have been accustomed to look for. 
6. The yellow rust appears in certain varieties of wheat and 
barley that are especially susceptible, uniformly four to five weeks 
after sowing. 
7. The intensity has sometimes been stronger in sunny than in 
shady places in the same wheat field. 
These two observations, together with the results from sev- 
5 Details will soon be published elsewhere. 
