Formation of perithecia in colonies of Podospora anserina.

The relationship between the staling of vegetative hyphal growth and the formation of perithecia was studied in Podospora anserina (Ces. in Rabenh.) Niessl. Enhanced numbers of perithecia were found on both sides of the contact line of two colonies, where forward growth ceased. If only part of the hyphal front was checked, an increase in the number of fruiting bodies also occurred. This check was achieved after penetration of the mycelium into a poor medium, by preventing the growth of the superficial mycelium, or by inducing zonations. L-sorbose, which inhibits hyphal elongation, also induced more protoperithecia.