Reed—Infection Experiments. 
137 
In his experiments, Neger found that the incubation period 
was two to three days. 
Neger raised the question whether this specialization which he 
discovered in the conidia of the mildews also extends to the asco- 
spores. He says he has never observed perithecia with the asco- 
spores formed on Senecio vulgaris, Galium silvaticum, Cala- 
mintha acinos, Symphytum tuberosum , Hieraceum murorum and 
others. The question arises how these plants become infected 
each spring. The conidia cannot live over the winter. Neger 
found that conidia from Plantago, if kept dry, lost their germi¬ 
nating power in seven days and conidia from Artemisia in 
twelve days. In order to explain the facts as observed by him, 
he advances the theory that the ascospores have the capacity to 
infect a wider range of host-plants than the conidia. To illus¬ 
trate this we might take the three host-plants, a, b, and c, the 
conidia of each constituting a well-defined physiological species. 
We may further assume that perithecia with ascospores may be 
formed only on a. In the spring, however, these ascospores may 
be capable of infecting all three host-plants, a, b, and c, and 
thus spread the fungus. 
If the ascospores have a wider range of host-plants than the 
conidia of the same species, the way in which the conidia become 
specialized each season has to be explained. Neger attempts to 
explain this by citing the experiment of Brefeld who found that 
the spores of certain smuts, if grown in a nutrient solution, lost 
their ability to infect a living plant. Ward also found that 
conidia of Botrytis cinera, if grown in an artificial nutrient sub¬ 
stance, could not infect turnips. It must be remembered, how¬ 
ever, that it is often a difficult thing to get spores to germinate 
in a nutrient solution and the plants produced are frequently 
not vigorous and so in turn do not produce a very high per cent 
of viable spores. 
Neger compares this assumed capacity of the ascospores to in¬ 
fect a wider range of host-plants than the conidia to a similar 
capacity which he claims exists in the aecidiospores of the rusts. 
On this point he cites the work of Eriksson (2) who found that 
Avena sativa and Alopecurus pratensis were both infected with 
aecidospores taken from the same aeeidum cup, the uredospores 
of each constituting distinct forms. It must be stated, however. 
