Note 191 — Chapter II · CONSTITUENTS OF THE LICHEN THALLUS

The authors quoted have been followed in their designation of the various green algae that form lichen gonidia. It is however now recognized (Wille 1913) that either Protococcus viridis Ag., Chlorella or other Protococcaceae may form the universal green coating on trees, etc., and be incorporated as lichen gonidia. Pleurococcus vulgaris Naeg. and Pleurococcus Naegeli Chod. are synonyms of Protococcus viridis. In that alga there is no pyrenoid, and no zoospores are formed.

The genus Cystococcus, according to Chodat (1913), is characterized by the presence of a pyrenoid and by reproduction with zoospores and is identical with Pleurococcus vulgaris Menegh. (non Naeg.), though Wille regards Meneghini’s species as of mixed content. Paulson and Hastings (1920) now find that Chodat’s pyrenoid is the nucleus of the cell.