Aug. 25, 1923 
Ophiobolus cariceti and Weakened Plants 
353 
land running along its entire width through which the fence row had 
previously passed; part of the fence still existed to the west of the wheat 
field. This row marked the southern edge of an incline, and to the south 
of it the area was quite level throughout, and of a different type of soil, 
as above stated. 
While Ophiobolus, both perithecia and mycelium, could be found scat¬ 
tered in the north end, a very careful search beyond the edge of the 
incline to the south failed to reveal a single plant with symptoms of 
Ophiobolus. The field was revisited several times; on one occasion the 
writers were accompanied by two other plant pathologists, Dr. A. G. 
Johnson and Mr. H. H. McKinney, and no evidence of attack by Ophio¬ 
bolus could be found by anyone south of the region where the fence row 
had existed. As will be fully described later, a number of wild grasses 
were also found badly attacked by Ophiobolus in this same strip. In 
spite of the excellent opportunity for infection taking place on both sides 
of this strip, the drill rows extending through from the poor soil to the 
good soil, infections were sharply confined to the wheat growing to the 
north upon the poor soil. Here, as on the Pool farm, there appeared 
to be a close correlation between the presence of weak, sickly plants and 
the pathogenicity of Ophiobolus. 
OPHIOBOLUS CARICETI ON WILD GRASSES 
In addition to wheat, the following grasses have been found attacked : 
Festuca octoflora , Festuca elatior, Bromus secalinus , Hordeum pusillum , 
and Chaetochloa geniculata. Dr. A. G. Johnson first detected signs of 
Ophiobolus on a wild grass in the diseased wheat fields near Prairie Grove, 
previously mentioned, and while no fruiting bodies were observed at the 
time, a careful inspection by the senior writer of material subsequently 
gathered on the same field revealed typical fruiting bodies on two wild 
hosts, Festuca octoflora and Bromus secalinus . (PI. 4.) 
In the same strip of soil where the fence had previously existed, as well 
as in other spots in the north end of the field, many plants of Festuca 
octoflora, Bromus secalinus, and Hordeum pusillum were found showing 
symptoms similar to the diseased wheat in the same vicinity. A thorough 
search for Ophiobolus on wild grasses near take-all diseased wheat on 
the Pool farm also brought to light many diseased plants of Festuca 
octoflora (a common grass in this locality), on some of which perithecia 
of Ophiobolus were found. 
As the presence of Ophiobolus on these wild grasses strongly suggested 
an organism more or less endemic in nature, a search was made for it in 
regions where wheat had not been grown. It was shortly after detected 
on unthrifty plants of perennial foxtail (Chaetochloa geniculata ), grow¬ 
ing in a few water-logged areas on the campus of the University of 
Arkansas. No further search was made, but as no wheat had ever been 
grown on the campus (used as such for about 50 years) there is no reason 
for doubting the endemic nature of Ophiobolus on this native grass. 
IDENTITY OF THE ASSOCIATED ORGANISM 
The question as to whether or not the species of Ophiobolus which at¬ 
tacks wheat is the same as that on the wild grasses was determined by a 
careful comparison of perithecia, asci, spores, and mycelium found on the 
different hosts. An illustration of the close morphological agreement may 
