1. Mycoidea Cunningh. (Cephaleuros Kunze). In Mycoidea parasitica the filaments of the disc are partly erect and partly decumbent, reddish to green ([Fig. 31]). It forms the gonidium of the parasitic lichen, Strigula complanata, which was studied by Marshall Ward in Ceylon[288]. Zahlbruckner gives Phyllactidium as an alternative gonidium of Strigulaceae.
2. Phycopeltis Millard. Disc a stratum one-cell thick, bearing seta, adnate to the lower surface of the leaf, yellow-green in colour. Phycopeltis ([Fig. 32]) has been identified as the gonidium of Strigula complanata in New Zealand and of Mazosia (Chiodectonaceae), a leaf lichen from tropical America.
Fig. 31. Mycoidea parasitica Cunningh. much magnified (after Marshall Ward).
There is some confusion as to the genera of algae that form the gonidia of these epiphyllous lichens. Phyllactidium given by Zahlbruckner as the gonidium of all the Strigulaceae (except Strigula in part) is classified by de Toni[289] as probably synonymous with Phycopeltis Millard, and as differing from Mycoidea parasitica in the mode of growth.
Fam. Prasiolaceae. Thallus filamentous, often expanded into broad sheets by the fusion of the filaments in one plane.
Prasiola Ag. Thallus filamentous, of one-to many-cell rows, or widely expanded ([Fig. 33]). The gonidium of Mastoidiaceae (Pyrenocarpeae).
Fig. 32. Phycopeltis expansa Jenn. much magnified (after Vaughan Jennings).