Fig. 7. Germination of spore of Physcia parietina De Not. in contact with Protococcus viridis Ag. × 950 (after Bornet).
Fig. 8. Physcia parietina De Not. Vertical section of thallus obtained by synthetic culture × 130 (after Bonnier).
Some years later Bonnier[198] made an interesting series of synthetic cultures between the spores of lichens germinated in carefully sterilized conditions, and algae taken from the open ([Figs. 7 and 8]). Separate control cultures of spores and algae were carried on at the same time, with the result that in one case lichen hyphae alone, in the other algae were produced. The various lichen spores with which he experimented were sown in association with the following algae:
(1) Protococcus.
Pure synthetic cultures of Physcia (Xanthoria) parietina were begun in August 1884 on fragments of bark. In October 1886 the thallus was several centimetres in diameter, and some of the lobes were fruited.
Physcia stellaris was also grown on bark; in one case both thallus and apothecia were developed.
Parmelia acetabulum, another corticolous species, formed only a minute thallus about 5 mm. in diameter, but entirely identical with normally growing specimens.
(2) Pleurococcus.