A Contribution Toward Lichen Synthesis

Abstract

The synthesis of lichens in the laboratory, beginning with the isolated algal and fungal symbionts, has long been the dream of lichenologists. Despite numerous attempts (a good history is given by Werner 1927) and a few reported successes (Bonnier 1889, Thomas 1939), the problem still remains unsolved and is as enigmatic today as it was some 90 years ago when the true nature of lichens was discovered. The experiments described in this paper have resulted in some interesting observations regarding the initial stages of lichen synthesis. Several of the results obtained deviate quite markedly from those published by earlier workers, notably those of Gaston Bonnier, who has claimed to have achieved many true lichen syntheses. Bonnier described synthetic culture in which 5 days after germination the clasping hyphae had laid hold of the algae and symbiotic growth had begun, a small lichen thallus being formed some 50 days later, with subsequent apothecial formation. In the light of my experiments this is indeed a remarkable feat. Bonnier's experiments contain numerous inconsistencies and unexplained points (Thomas 1939, p. 187); these, coupled with the fact that no one has been able to duplicate his experiments, make one hesitant in accepting his results. The lichen used for our experiments was Lecanora dispersa (Pers.) Rohl., an urban, saxicolous form growing quite conveniently on the concrete ledge of the basement window of the Farlow Herbarium. The procedure, carried out under sterile conditions and using sterile apparatus and cultures, may be outlined as follows: A non-nutrient agar (Noble's Agar) containing Knop's mineralsolution medium (pH 7.3) was employed. Immediately after autoclaving, this medium was pipetted into a van Tieghem cell and a carefully washed cover-slip was then placed over this filled cell and lifted off again