218 
Vol. XXIX, No. 5 
Journal of Agricultural Research 
According to Eriksson and Henning 
(4), the urediniospores of Puccinia 
glumarum , like those of P. gra minis, 
produce a germ tube of fairly uniform 
diameter. It is almost invariably un¬ 
branched and contains throughout its 
length the yellow contents of the spore. 
Where germination takes place on the 
surface of a living host leaf, there de¬ 
velops at once an appressorium from 
which is derived the infecting thread 
or hypha which enters a stoma to pro¬ 
liferate later and form successive 
masses of mycelium or liymenia which 
give rise to uredinia and a new crop of 
urediniospores. Throughout the vege¬ 
tative period of the host, the disease 
spreads from leaf to leaf and ultimately 
echinulate and varies in thickness from 
about 1 fj to 2 /z. The four to several 
germ-pores occur irregularly and, ex¬ 
cept under very favorable optical con¬ 
ditions, are seen with difficulty (fig. 4). 
According to Eriksson and Henning 
(4), the urediniospores measure from 
16 to 19 m by 25 to 30 ix in diameter. 
Grove ( 6 ), on the other hand, gives 
the dimensions as varying from 18 to 
26 fx by 25 to 30 m- As will be seen 
from Table I, the writers’ figures, 
based on the measurement of 10,000 
spores, show a variation of 12.7 to 
25.9 fx by 15.7 to 33.8 m- The average 
of 10,000 long and short diameters was 
22.63 fx and 18.40 /x, respectively. The 
wide differences in the two diameters 
Fi<i. 4.—Camera lucida drawings of urediniospores of Puccinia glumarum on, a, Triticum rulgare; b, T 
durum ; c, Ilordeum jubatum; and d, Elymus canadensis. X 1000 
to the entire plant. Under particularly 
favorable conditions in spring and 
early summer the amount of initial in¬ 
fection and subsequent development of 
stripe rust in any one season may be 
considerable and result in severe 
damage to the crop. 
Marryat (18) states that infection re¬ 
sulting from P. glumarum obtains, as in 
the case of P. graminis ,'through en¬ 
trance of the stomata by the germ 
tubes of the urediniospores. 
UREDINIOSPORES 
The urediniospores of Puccinia glum¬ 
arum, sometimes accompanied by liy- 
phoid, incurved paraphyses, vary in 
form from globose to broadly ellipsoid. 
The colorless spore wall is moderately 
would seem to indicate the possible im¬ 
maturity of some of the spores. Care 
was exercised in every instance, how¬ 
ever, to confine the measurements to 
those which were fully mature. Sub¬ 
sequent to the preparation of the data 
presented in Table I, it was found that 
the size of the urediniospores ap¬ 
parently is governed to some extent by 
position on the infected leaf and con¬ 
sequent availability of nutriment. For 
example, 100 spores from uredinia 
near the base of a rusted leaf of Baart 
wheat averaged 18.90 ix by 25.64 m; a 
similar number from the middle of the 
leaf averaged 18.71 u by 24.84 fx while 
100 spores from uredinia at the outer 
end of the leaf averaged 18.54 ix by 
23. 12 fx. 
