Nov. 1, 1925 
Ophiobolus graminis and Take-All of Wheat 
805 
However, Delacroix (8) made further observation in an attempt to verify 
Mangin’s work, but failed to find promycelia and sporidia. He sug¬ 
gested that Mangin probably had another species of Ophiobolus. 
In the course of the present studies, no spore forms other than 
ascospores have been found. Paraphyses were present in the peri¬ 
thecia during ascus formation, but as the spores matured they 
disappeared. Perithecia in which the asci were well developed, but 
in winch no spores were differentiated, contained paraphyses. The 
paraphyses were hyaline, three to four celled, slightly broader at 
the base than at the tip, and rather irregular in shape.* When the 
ascospores were formed, the paraphyses disappeared. Apparently 
they were absorbed to furnish food for the developing spores, as no 
trace of them could be seen in any fully matured perithecium. 
The mycelium was found to be extremely variable both in general 
appearance and diameter of hyphae, but this was probably due in part 
to age and conditions of growth. In rapidly growing cultures a line, 
hyaline mycelium with granular protoplasm and few or no cross¬ 
walls was very abundant. As the hyphae became older, they in¬ 
creased in diameter, the walls became brown in color, and numerous 
Fig. 2—Fine hyaline mycelium developed at a broken end of a coarse brown hypha of Ophiobolus graminis . 
_ Drawn with aid of a camera lucida. X 1,000 
septa were formed, the protoplasm lost its granular appearance, and 
oil droplets appeared in the cells. Furthermore, an injury to a 
coarse hypha often would induce the formation of a new hypha at 
the point of injury. This new mycelium invariably had a much 
smaller diameter than the old, as shown in Figure 2. With ordinary 
staining methods the fine mycelium readily took up and retained the 
stain, while the coarse type did not hold the stain well. Very often the 
mature hyphae adhered closely together and formed strands. As many 
as 6 hyphae have been seen united in this manner, and when attempts 
were made to separate them the whole strand often broke crosswise. 
As stated previously, pure cultures of the New York strain of 
the fungus formed numerous mature perithecia when grown on arti¬ 
ficial media. However, the Oregon and Arkansas strains of the 
parasite never produced mature fruiting bodies when handled in the 
same manner as the New York strain. In some cases perithecium- 
like bodies were produced, but these were never found to contain 
asci or ascospores. When the Oregon and Arkansas strains were 
planted on opposite sides of a Petri dish containing solid medium, 
they seldom grew together. When they did, however, the hyphae 
were much darker in color along the line where the two mycelia met 
than elsewhere, but in no case did mature fruiting bodies develop in 
these dishes. Likewise each strain was planted in Petri dishes with 
the New York strain, and also all three strains were planted in the 
same dish. Dark lines developed at the juncture of the colonies in 
each case, but perithecia were produced only where the New York 
strain touched the other strains and in concentric circles about the 
center of inoculation in the colonies of this strain (pi. 1, B). 
