356 
Journal of Agricultural Research 
Vol. XXV, No. 8 
a great deal of attention. The yield of the control plot was com¬ 
parable to that obtained by Mr. Pool on the same area the previous year. 
DISCUSSION 
The writers have no satisfactory explanation to offer for the presence 
of the Ophiobolus on some of the plants of the manure as well as the com¬ 
mercial fertilizer plots, but whatever such an explanation may be, it is 
clear that irrespective of the presence of the fungus the yields on these 
plots as compared with those on the untreated and lime plots were so 
satisfactory that for practical purposes these treatments, particularly the 
commercial fertilizer, may be considered as having almost completely 
controlled the disease. The percentage of infection on the manure and 
commercial fertilizer plots as compared with that on the check and lime 
plots was so strikingly different that there can be no question that the 
parasitism of Ophiobolus was greatly inhibited. Why commercial ferti¬ 
lizer gave better control than manure can not be answered at this time, 
but it is perhaps safe to conclude that control may be not entirely a matter 
of a sufficient amount of nutrients. 
The pathogenicity of Ophiobolus cariceti (0. graminis) on healthy plants 
has been questioned by various investigators previous to this time. 
From Stevens' (io) excellent summary of the literature on wheat footrots, 
including Australian take-all, the following references may be noted: 
Pearson (9) in 1888 decided that this is a poverty disease, “and that the 
fungus which causes take-all attacks mainly such crops as are insuffi¬ 
ciently nourished." Tepper (12) in 1892 said that “Take-all is nothing 
else than starvation of the crop. ’ ’ Me Alpine (7) in 1902 stated that ‘ ‘ Take- 
all largely depends on the nature of the season and the mechanical condi¬ 
tion of the soil. * * * If the soil is neither too dry * * * nor so wet 
as to cake * * * and contains sufficient plant food * * * then 
the take-all will not appear." Voges (14-18) in a number of articles run¬ 
ning over a period of years up to 1914 concludes that Ophiobolus is not 
the primary cause of the disease, but, judging from his descriptions, it may 
be doubted whether he had studied the Ophiobolus disease which is 
described by Me Alpine and others as common in Australia. Various other 
investigators who have associated Ophiobolus with this disease have con¬ 
cluded that conditions which tended to weaken the plants, such as frost, 
wet weather, poor soil, etc., rendered the plants susceptible to attack by 
this fungus. Most of them, however, rely almost entirely on field obser¬ 
vations, and little or no attempt has been made to study these relation¬ 
ships under rigid experimental conditions with adequate controls. 
Contrary to the opinion that Ophiobolus attacks only weakened plants, 
the recent paper by Kirby (5) presents the view that the fungus is a vig¬ 
orous parasite capable of attacking healthy plants, and cites the work of 
other investigators who express or imply similar views. Inasmuch as 
Kirby's work is much more thorough and exact than that of any of the 
others it may suffice to analyze his work. Using pure cultures of Ophiobo¬ 
lus cariceti growing on wheat kernels, he inoculated 156 pots of wheat at 
planting time and noted that at maturity the plants in all the inoculated 
pots showed typical symptoms of take-all, while no plant in any of the 78 
control pots exhibited such symptoms. From the inoculated plants he 
then recovered the same fungus. As far as this evidence is concerned, 
there appears to be no doubt that Ophiobolus cariceti can attack wheat 
and other grasses, but the question that one asks after reading his paper 
carefully is, What was the condition of the wheat, inoculated or uninocu- 
