Dec. 3,1917 
Podblight of Lima Bean 
481 
The pycnidia vary greatly in size (158.0 to 475 /z, average 245.86 fx 
from host). They are irregular in shape, chambered with an inner 
hyalin layer from which the conidiophores arise, and a dark outer layer 
much thickened and darkened above (PI. 43, B, C), all characters typical 
of the genus Phomopsis. Sometimes the contiguous sidewalls of two or 
more pycnidia are ruptured, forming a single cavity (PI. 43, E). On the 
other hand, they may be pressed together but separated by a single dark 
wall and their respective hyalin inner layers, thereby 
forming a chain of pycnidia (PI. 43, C). The pyc¬ 
nidia can hardly be said to be embedded in a true 
stroma. 
The pycnidia on the leaves and stems are lenticu¬ 
lar in shape, rarely, or not at all chambered (PI. 43, 
A), fewer in number, and smaller than on the pods 
and usually isolated. They vary in size from 197.5 to 
260.0/z, average 219.0 ju. 
The pycnospores are borne on slender, hyalin, sim¬ 
ple conidiophores (fig. 2, a), 1% to 3 times the length 
of the pycnospore. They are mostly oblong to fusoid 
(fig. 2, b; 3), hyalin, 1-celled, usually straight, seldom slightly curved, 
with two large oil droplets. These droplets, sometimes pressed to¬ 
gether in the center of the spore, give the appearance of a septum, a 
characteristic common to the genus Phomopsis and so deceptive that 
at a casual glance one might believe that a true septum was laid down. 
That the spore is but 1-celled can readily be demonstrated by clearing 
it with a little salicylic acid. The variation in the size of 
the pycnospores from various sources is seen from the 
following measurements: 
^ ^ W From host.—6.0 to 8.6 by 2.4 to 4.1 fx, average 7.5 by 
Big. 2 .—Diaporthe phas- 
eolorum: Long, slender, 
fragile sporophores with 
two pycnospores at¬ 
tached. (a) Sporo¬ 
phores; (6) pycno¬ 
spores. X500. 
Big. 3. — Diapor- 
t he phaseol&- 
rum: A group of 
pycnospores. 
Note the oil 
droplets and 
variations i n 
3-23 M- 
Stems of MelUotus alba. —5.6 to 10.0 by 2.4 to 4.0 /z, 
average 7.82 by 3.11 fx. 
Com meal.—5.4 to 8.2 by 2.4 to 3.4 /z, average 6.49 by 
2.79 ix. 
size and shape. Irish potato cylinders.—5.4 to 8.5 by 1.7 to 3.0 ix, aver- 
s °°* age 6.36 by 2.59 /z. 
Corn-meal agar.—5.1 to 8.3 by 2.4 to 3.4 /z, average 6.78by 2.85 /z. 
Rice.—5.4 to 8.5 by 2.0 to 3.4 fx t average 6.45 by 2.80 fx. 
It wdl be noted that the spores are relatively large in artificial cul¬ 
tures on stems of Melilotus alba , and small on cooked Irish potato cyl¬ 
inders. This difference has been found rather constant, and is prob¬ 
ably associated with vigor of growth. Of all media tried stems of 
M. alba were found exceedingly favorable for spore formation, while 
cooked Irish potato cylinders were rather unfavorable. 
23716°—17-3 
