Many of the freshwater algae which form a mere crust, such as Palmella cruenta, may be placed in a vessel of water, where after a time they float like a scum, the earthy matter settling down to the bottom, and may then be mounted by slipping a piece of mica under them and allowing it to dry.
Usnea, Cladonia, Physcia, Parmelia, Calicium, many species of Lecidea, &c., Trentepohlia (Chroolepus) umbrina in many species of Verrucaria, Graphidieae and Lecidea; Palmella botryoides in Epigloea; Pleurococcus vulgaris in Acarospora, Dermatocarpon, Catillaria; Dactylococcus infusionum in Solorina, Nephromia; After Sachs, from De Bary's Vergleichende Morphologie and Biologie der Pilze, Mycetozoen and Bacterien, by permission of Wilhelm Engelmann.
With Pleurococcus or Palmella gonidia.
Mycoporaceae with Palmella_or Chroolepus gonidia.
Again, many Green Algae - some unicellular, like Sphaerella and Chlamydomonas; some colonial forms, like Volvox and Hormotila: some even filamentous forms, like Ulothrix and Stigeoclonium- are known to pass into a condition resembling that of a Palmella, and might escape identification on this account.