Zukal has considered that the lichen acids protect the lichen from the attacks of animals; the experiments of Zopf, however, have cast doubt on this; certainly lichens containing very bitter acids are eaten by mites though some of the acids appear to be poisonous to frogs.
Zopf, " Vergleichende Produkte," Beitr.
Teil (1892 onwards); Zopf, Die Pilze (Breslau, 1890); De Bary, Comparative Morphology of Fungi, &c. (Oxford, 1887); von Tafel, Vergleichende Morphologie der Pilze (Jena, 1892); Brefeld, Ureters.
Spores and Sporophores: Zopf, Die Pilze; also the works of von Tafel and Brefeld.
The supposed constancy of forms in Cohn's species and genera received a shock when Lankester in 1873 pointed out that his Bacterium rubescens (since named Beggiatoa roseo-persicina, Zopf) passes through conditions which would have been described by most observers influenced by the current doctrine as so many separate " species " or even " genera," - that in fact forms known as Bacterium, Hicrococcus, Bacillus, Leptothrix, &c., occur as phases in one life-history.
(After Zopf.) A.
Zoogloea of Bacterium merismopedioides, Zopf, containing cocci arranged in tablets.
Broad according to Zopf), highly refractive and colourless (or very dark, probably owing to the high index of refraction and minute size).
Zopf in 1885 proposed a scheme based on the acceptance of extreme views of pleomorphism; his system, however, was extraordinarily A FIG.