6 
WALTER SPURGEON BEACH 
The denominators of the adjacent fractions state the total number of leaves 
inoculated, and the numerators the number of leaves having one or more 
infected spots. The total number of spots formed is given in the tables 
where this is required for a closer comparison of susceptibility. In the 
second column of each table the letter / indicates that the experiment was 
conducted in the field or out of doors, and g that it was carried on in the 
greenhouse. The letter b with the accompanying figure records the number 
of days the plant was bagged immediately following inoculation. 
The lists of hosts given were compiled partly from Saccardo's "Sylloge 
Fungorum," and partly from data furnished by the herbaria of the New York 
Botanical Garden and the United States Department of Agriculture. 
Septoria polygonorum Desm. 
All collections of Septoria made from species of Polygonum at Urbana 
^re determined as Septoria polygonorum Desm. This fungus has been 
rted upon the following species of Polygonum, which are arranged in 
or o. 
bsefected by the author 
P. persicaria 
" pennsylvanicum 
" lapathifolium 
' ' orientate 
C. Not used in experiments 
P. historta 
sieholdii 
' ' mitis 
hydropiperoides 
" muhlenbergii 
" dumetoruni 
The members of group C are foreign, oi were not found growing in this 
vicinity. The species of group B, as well as others that gave negative 
results when inoculated, apparently had sufficient opportunity to become 
infected in nature; for infected plants of smartweed were usually growing 
in close proximity to the uninfected kinds. Yet repeated search for material 
resulted in finding Septoria polygonorum upon only Polygonum persicaria, 
P. pennsylvanicum, and P. lapathifolium, upon which the form in this 
locality appears to be specialized. The plants of P. orientate were few and 
apparently escaped infection by being isolated. It remains an open question 
whether the forms of Septoria polygonorum reported upon P. amphibium, 
P. hydropiper, and P. convolvulus of group B are differently specialized or 
whether the hosts are resistant in this region. The former case is likely if 
the fungi and their hosts were correctly determined. 
B. Inoculated but not infected 
P. amphibium 
" hydropiper 
convolvulus 
D. Synonymous 
P. incarnatum = P. lapathifolium 
" nodosum = P. lapathifolium 
