Lecanora (Rinodina) sophodes, sown on rock in 1883, reached in 1886 a diameter of 13 mm. with fully developed apothecia.
Lecanora ferruginea and L. subfusca after three years’ culture formed sterile thalli only.
Lecanora coilocarpa in four years, and L. caesio-rufa in three years formed very small thalli without fructification.
(3) Trentepohlia (Chroolepus).
Opegrapha vulgata in two years had developed thallus and apothecia. The control culture of the spores formed, as in nature, a considerable felt of mycelium in the interstices of the bark, but no pycnidia or apothecia.
Graphis elegans. Only the beginning of a differentiated thallus was obtained with this species.
Verrucaria muralis (?)[199] gave in less than a year a completely developed thallus.
Bonnier also attempted cultures with species of Collema and Ephebe, but was unsuccessful in inducing the formation of a lichen plant.
H. Hymenial Gonidia
Reference has already been made to the minute green cells which were originally described by Nylander[200] as occurring in the perithecia of a few Pyrenolichens as free gonidia, i.e. unentangled with lichen hyphae. Fuisting[201] found them in the perithecium of Polyblastia (Staurothele) catalepta at a very early stage of its development when the perithecial tissues were newly differentiated from those of the surrounding thallus. The gonidia enclosed in the perithecium differed in no wise from those of the thallus: they had become mechanically enclosed in the new tissue; and while those in the outer compact layers died off, those in the centre of the structure, where a hollow space arises, were subject to very active division, becoming smaller in the process and finally filling the cavity. Winter’s[202] researches on similar lichens confirmed Fuisting’s conclusions: he described them as similar to the thalline gonidia but lighter in colour and of smaller size, measuring frequently only 2·3 µ in diameter, though this size increased to about 7 µ when cultivated outside the perithecium.