The perithecia are only produced exceptionally in Europe, but this stage of the life-history is common in the United States and causes a widely spread disease among the American vines.
Portion of vine root, showing masses of fructification (perithecia) of the fungus (reduced).
Most systems agree in deriving the major divisions from the characters of the reproductive organs (perithecia, apothecia, or basidiospore bearing fructification), while the characters of the algal cells and those of the thallus generally are used for the minor divisions.
Perithecia divided or imperfectly divided by cross-walls.
The reproductive spores are formed in embedded flesh-shaped receptacles (perithecia) and scattered after the leaves have fallen.