10 BULLETIN 1347, U. S. DEPARTMENT OF AGRICULTURE 
In comparing the ascospores and perithecia of several strains of 
Ophiobolus obtained on wheat from various localities in this country 
with the three original descriptions under consideration, it seems evi- 
dent that we are dealing with O. graminis Sacec. The writer has 
noted some variations in the size of spores in the several strains of 
O. graminis being studied, but such variations have not tended in the 
direction of O. cariceti, nor have they yet been found to vary to the 
extent that they reached the length recorded for O. eucryptus. 
Rather extreme variations in the size and shape of the perithecia 
of Ophiobolus graminis also have been noted by the writer, and it 
has been found that the frequently smooth pycnidia of Wojnowicia 
graminis (McAlIp.) Sace. and D. Sacc. are in many cases indistin- 
euishable from the perithecia of O. graminis both with respect to 
form and position on the host. Frequently the pycnidia of W. 
graminis and the perithecia of O. graminis are found on the same 
plant, and the pycnidia often occur independently on diseased wheat 
plants in the areas where 0. graminis occurs. As yet our own studies 
have not advanced to the point where we can be certain that we are 
dealing with O. graménis on diseased wheat plants until the contents 
of mature fruiting bodies have been examined microscopically. The 
writer knows of no published work giving descriptions or methods 
which will assist in distinguishing with certainty the perithecia of 
O. graminis from many of the pyenidia of W. graminis, and all 
observations which have been made by him indicate that any attempt 
to identify O. graminis on a basis of the perithecia, as suggested by 
Fitzpatrick, Thomas, and Kirby (27), is likely to lead to error. 
As the problem of nomenclature of the take-all fungus now stands, 
it appears that ascus-bearing type material of Ophiobolus eucryptus 
and (. cariceti is no longer in existence, and therefore the original de- 
scriptions and drawings of these species are our only means of 
identification. On the basis of these descriptions and on that of 
Saccardo for O. graminis it is only reasonable to consider that all 
three species are distinct, and as the Ophiobolus, which the writer 
and many other workers, including Fitzpatrick, Thomas, and Kirby 
(27), have found to cause the take-all disease essentially conforms 
to Saccardo’s description, the writer will continue to designate it by 
the widely accepted name Ophiobolus graminis Sacc. 
Ophiobolus graminis was considered the cause of a foot-rot in 
Europe and take-all in Australia for a number of years before the 
experimental proof was presented. Mangin (50) and Delacroix 
(17), working in France, carried out inoculation experiments which 
indicated rather clearly that this organism causes the disease in 
question. In these experiments these workers obtained ascospores 
of the fungus from perithecia produced on diseased plants. They 
prepared water suspensions of these ascospores and applied them to 
soil in which wheat plants were growing. In the case of Mangin’s 
experiments infection was somewhat delayed, but after replanting 
in the inoculated soil he obtained the disease. Delacroix found, more 
readily than did Mangin, that O. graminis produced typical foot- 
rot (take-all) symptoms. Plants growing under the same condi- 
tions but in uninoculated soils remained healthy. While all the 
plants growing in Delacroix’s inoculated soil did not become in- 
fected, those which did showed the typical symptoms of take-all. 
