aeciospore

(aecidiospore) A dikaryotic spore formed by certain rust fungi in a small cup-shaped sorus, the aecium or aecidium. The aeciospores of Puccinia graminis are formed on the lower surfaces of barberry leaves in clusters of aecia, this stage of the life cycle commonly being called the cluster-cup stage. The aeciospores cannot reinfect barberry but will germinate on certain grass or cereal leaves where the subsequent infection shortly gives rise to *uredospores. See heteroecious.