12 BULLETIN 1347, U. S. DEPARTMENT OF AGRICULTURE Pr 
cultural behavicr of these two forms is sufficiently different to cause 
one to doubt any genetic connection between them. 
Kirby (37) reports that the ascospores of Ophiobolus graminis live 
through the winter in the soil. Davis® confirms this. He also 
found that the mycelium survives the winter. Many workers seem 
to consider that O. graminis infects chiefly, if not entirely, by means 
of its ascospores, but no doubt the mycelium is of importance also, 
especially as several workers (37, 73) have shown that the fungus 
mycelium can live saprophytically for a time at least and that the 
mycelium is infectious. Further data are needed on the relative im- 
portance of ascospores and mycelium as infective agents. Informa- 
tion is also lacking on the relative importance of ascospores and my- 
celium as hold-over infective materials. It seems well to consider the 
possible importance of the vegetative stage of the fungus under field 
conditions. General field observations indicate that the fungus can 
not exist long as a saprophyte, but experimental evidence on this 
point is lacking. 
The writer has noted some irregularity in the habits of this fun- 
gus with regard to the production of fruiting bodies. This has 
been especially noticeable in the take-all experimental plats located 
at Abilene, Kans., and on the agronomy plats located on the experi- 
ment station farm at Manhattan, Kans. During the past four years 
the symptoms of take-all have developed in a more or less typical 
vay at Abilene, but not until 1923 did the writer find the mature 
perithecia of the fungus, and then the fruiting bodies were very 
scarce and difficult to find. Doubtless perithecia had developed 
previously, but they were not found. In Oregon it has been noted 
that the fruiting bodies of the fungus do not develop as frequently 
in some years as in others. The writer examined take-all plants 
collected near Corvallis, Oreg., in 1921, and found that perithecia 
were very sparse. In 1923 take-all plants were collected by H. 
Fellows in a field adjacent to the one observed in 1921, and fruiting 
bodies were found to be exceedingly abundant. These observations 
are borne out in a measure by McAlpine (47), who states that “ In 
dry seasons and during certain periods of the year only the vegeta- 
tive portion of the fungus may be found * * *.” If perithecial 
development is influenced by seasonal factors it probably is also 
affected by climatic differences in different localities. Take-all 
material collected in North Carolina and New York shows an abun- 
dance of fruiting bodies on a large proportion of the diseased stalks. 
Kirby (38) has stated that Ophiobolus graminis is heterothallic, 
which, if true, would explain some of the irregularities cited in con 
nection with the production of perithecia. However, the studies by 
Davis indicate that more evidence must be presented before the 
occurrence of heterothallism in QO. graminis is fully established. 
In certain strains of this fungus Davis has shown clearly that hetero- 
thallism does not exist. 
FACTORS INFLUENCING THE DEVELOPMENT OF TAKE-ALL 
Many statements are found in foreign literature regarding the 
influence of weather and seasonal conditions on the foot-rots and 
8 Davis, R. J. Studies on Ophiobolus graminis Sace. and the TakeAll Disease of 
Wheat. (Unpublished manuscript.) 
