. Lichens. Lichens. LICHEN ALGAE 59 Earn. Trentepohliaceae. Filamentous and branched, the filaments short and creeping or long and forming tufts and felts or cushions; colour, brownish-yellow or reddish-orange. Trentepohlia Born. Branching alternate; cells filled with red or orange oil; no pyrenoids (Fig. 29). A large number of lichens are associated with this genus : Pyrenulaceae, Arthoniaceae, Graphidaceae, Roccellaceae, Thelotremaceae, Gyalectaceae and Coenogoniaceae, etc., in whole or in part. Two species have been determined, T. umbrina Born., the gonidium of the Graphidaceae, and T. aure
. Lichens. Lichens. LICHEN ALGAE 59 Earn. Trentepohliaceae. Filamentous and branched, the filaments short and creeping or long and forming tufts and felts or cushions; colour, brownish-yellow or reddish-orange. Trentepohlia Born. Branching alternate; cells filled with red or orange oil; no pyrenoids (Fig. 29). A large number of lichens are associated with this genus : Pyrenulaceae, Arthoniaceae, Graphidaceae, Roccellaceae, Thelotremaceae, Gyalectaceae and Coenogoniaceae, etc., in whole or in part. Two species have been determined, T. umbrina Born., the gonidium of the Graphidaceae, and T. aurea which is associated with the only European Coenogoniuvi, C. ebeneuiii (Fig. 3). Deckenbach^ claimed that he had proved by cultures that T. umbrina was a growth stage of T. mirea. » Fam. Cladophoraceae. Filamentous, variously and copiously branched, the cells rather large and multinucleate. Cladophora Kiitz. Filaments branching, of one-cell rows, attached at the base; colour, bright or dark green ; mostly aquatic and marine (Fig. 30). Only one lichen, Racodium rupestre, a member of the Coeno- goniaceae, is associated with Cladophora. It is a British lichen, and is always sterile. Fam. Mycoideaceae. Epiphytic algae consisting of thin discs which are composed of radiating filaments. 1. Mycoidea Cunningh. (Cephaleuros K^unze). In Mycoidea parasitica the filaments of the disc are partly erect and partly decumbent, reddish to green (Fig. 31). It forms the goni- dium of the parasitic lichen, Strigida complanata, which was studied by Marshall Ward in Ceylon^. Zahl- bruckner gives Phyllactidium as an alternative gonidium of Strigula- Fig. 31. Mycoidea parasitica Cunningh. much magnified (after Marshall Ward). ceae. 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 Strigida complanata in New Zealand and of Mazosia (Chiodectonaceae), a leaf li
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