220 
Journal of Agriculutral Research 
Vol. XXIX, No. 5 
Levine (16) has shown that although 
resistant host plants and adverse en¬ 
vironmental conditions always tend to 
dwarf the spores of Puccinia graminis 
tritici, regardless of the physiologic 
form, this reduction in size is not per¬ 
manent. He has shown that when 
cultures from such spores are main¬ 
tained under normal growth conditions 
the resultant spores are of character¬ 
istic size and shape. The same con¬ 
dition also doubtless holds for the 
spores of P. glumarum. 
TELIOSPORES 
The teliospores of Puccinia glumarum 
develop in hypophyllous or culmico- 
lous sori. They occur in long, narrow 
lines; and in those wheat varieties 
where glume infection is common, form 
oblong blackish patches, in all cases 
covered by the epidermis. The spores, 
commonly 2-celled, are clavate to 
rounded or obliquely conical above, 
with smooth exospore which varies in 
thickness from about 1 m to 3-6 u for 
the thickened apex (fig. 5). The} 7 
are brown, somewhat constricted, at¬ 
tenuate at the base, and measure, ac¬ 
cording to Eriksson and Henning ^(4). 
16 to 24 At wide by 30 to 40 ju long. In 
his description of the teliospores 
Grove (6) gives a width varying from 
12 to 24 u and a length of 30 to 70 ,u. 
The writers’ figures, derived from the 
measurement of thousands of mature 
teliospores, approach more nearly those 
of Grove, and vary from 12 to 27 m 
by 30 to 65 m- The spores, borne on 
pale, short and usually persistent 
pedicels, occur in groups surrounded 
by long sterile curved cells or 
paraphyses. According to Arthur 
(1, p. 338-339) the teliospores germi¬ 
nate at maturity. 
Seed infection of wheat by Puccinia 
glumarum , which was first reported by 
Eriksson and Henning (4) and later by 
Blaringhem (3), has been noted by the 
writers most commonly in certain 
varieties, particularly Chul. The in¬ 
fection occurs in the pericarp of the 
wheat kernel, where it develops as 
mycelial pockets containing either 
urediniospores or teliospores or both 
(fig. 2). 
This seed infection suggests potential 
importance from the standpoint of 
seed transmission, which problem is 
being investigated by one of the writers 
(Hungerford) and the results will be 
published separately. 
THE FUNGUS IN RELATION TO DE¬ 
VELOPMENT OF THE DISEASE 
0 
SEASONAL OCCURRENCE 
As is true of other cereal rusts, stripe 
rust reacts to the conditions imposed 
upon it by temperature, relative hu¬ 
midity, soil, and other factors affecting 
the growth of both parasite and host. 
The absence of an alternate host and 
the relatively short period of viability 
of the urediniospores mak:e more or 
less fortuitous the occurrence of gen¬ 
eral and destructive outbreaks of this 
rust. Given a source of inoculum of 
sufficiently wide distribution, accom¬ 
panied by a combination of high rela¬ 
tive humidity, relatively low fall tem¬ 
peratures, and complete susceptibility 
of host, a general and severe outbreak 
of seedling infection may develop dur¬ 
ing the fall. If the crop is sufficiently 
protected from alternate freezing and 
thawing during the winter to prevent 
winter killing, the mycelium of the 
rust fungus will hibernate and be 
present as a potential factor for the 
development of new urediniospores 
the following spring. 
From the observational data in 
hand it is apparent that the further 
development and spread of stripe rust 
during the spring depend primarily on 
continuous high humidity and rela¬ 
tively low temperatures. On the other 
hand, it is true that a much more critical 
examination of meteorologic data and 
of other information bearing a possible 
relation to infection and spread of 
stripe rust in both the United States 
and Europe will need to be made be¬ 
fore it can be stated very certainly 
what combination of conditions most 
definitely determines the seasonal oc¬ 
currence and severity of stripe rust. 
VIABILITY AND LONGEVITY OF SPORES 
The literature extant on stripe rust 
contains but scant information on the 
duration of viability of the spores of 
Puccinia glumarum. Investigators, 
studying the problem of seasonal prop¬ 
agation of the rust, have emphasized 
the importance of hibernating myce¬ 
lium, and have shown that even in the 
far northern countries of Europe, stripe 
rust may, and frequently does, survive 
the vicissitudes of winter as viable my¬ 
celium within the tissues of the host 
