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 lichen from tropical 

 America. 



' Deckenbach 1893. 



^ In a comparative study of leaf algae from Ceylon and Barbadoes, N. Thomas (1913) came to the 

 conclusion that Marshall Ward's alga in its early stages is the same as Phyllactidium iropicum 

 Moebius ; and that the Barbadoes alga with which she was working represented the older stages, it 

 being then subcuticular in habit, forming rhizoids, barren and sterile aerial hairs and subcuticular 

 zoosporangia. 



