FIG. 18.

Asexual sporulation cycle of A. nidulans. Asexual sporulation of A. nidulans involves two phases: a vegetative growth phase, in which spore germlings give rise to hyphae and the mycelium, and an asexual reproductive phase, in which specialized hyphal cells called foot cells give rise to aerial stalks that produce spore-bearing structures called conidiophores. Stalks produce a vesicle that buds to produce branching cells called sterigmata. Further mitotic divisions of secondary sterigmata called phialides give rise to chains of conidia which germinate on an appropriate medium to complete the cycle.