Although lichens can reproduce sexually, they are predominantly asexual reproducers. In the latter case, small powdery clusters of hyphae and algae, called soredia are formed and cut off from the thallus as it grows. These soredia are dispersed by wind or water and take up residence elsewhere. Sexual reproduction occurs when the fungal ascomata produce spores which germinate and parasitize independently living algae upon contact with them. Lichen algae reproduce by mitosis and simple cell division.