On each of these host-plants the fungus has become specialized so that the form on barley cannot infect the other three cereals or the wild grasses and so on.
They appear to be present in large numbers in the soil, and to infect the Leguminous plant by attacking its root-hairs.
The conidia are fragrant and are carried by bees to the stigma of the bilberry; here they germinate with the pollen and the hyphae pass with the pollen tubes down the style; the former infect the ovules and produce sclerotia, therein reducing the fruits to a mummified condition.
Heteroica, is heteroecious; the ascospores infecting the leaves of Vaccinium uliginosum, while the conidia which then arise infect only Ledum palustre.
Close and continuous contact of plague-infected animals with healthy ones does not infect the latter if fleas are excluded.