Cicinnobolus Cesatii, a Study in Host-Parasite Relationships

The common parasite of the powdery mildews, Cicinnobolus Cesatii De Bary, has been known since the appearance of the grape mildew in England and Europe near the middle of the last century. The intimate association of Cicinnobolus with its host makes it a favorable object for the study of host-parasite relationships. It is, at least in its earlier stages, primarily an intracellular parasite which can be followed through its development in situ. The hyphae of the mildew are large and transparent and can be successfully studied in cytological preparations and in the living condition. It is also favorable material for the study of pycnidium formation in the transformed mycelial hyphae, conidiophores, and ascocarps of its host, and in cultures on artificial media. The earliest references to Cicinnobolus are descriptions of its pycnidia and spores given by students who believed that they were describing accessory spore forms of its host, Oidium or Erysiphe. The descriptions given by Amici (1853), Berkeley (1851, 1853, 1855, 1857), Figuier (1865), Montagne (1855), Graham (1851), Halstead (1888), and Cooke (1906) are of this sort. Savi (1853), Castagne (Montagne, 1855), and Crocq (1851) made the parasite the diagnostic feature of the mildew, which was then placed by each of them in a different genus. Both the Tulasnes (1861), and Von Mohl (1854) give excellent drawings of the pycnidia, but they considered them to be reproductive organs of the mildews. Cesati (1852) recognized the fungus as distinct from grape mildew and named it Ampelomyces quisqualis. Riess (1852) also observed it and called it Byssocystis textilis, and Ehrenberg (1853) gave it the name Cicinnobolus florentinus. However a number of students, including the Tulasnes and Von Mohl as noted above, continued to regard it as. a phase in the development of the mildew. De Bary (1870) was the first to make a thorough study of the fungus. He rejected the names which had already been given to it as unsuitable without making his reasons for doing so very explicit, and gave the fungus the name of Cicinnobolus Cesatii under which it has since been known. In a few cases later investigators have used the earlier name given by Cesati. Most of De Bary's observations were on the fungus as a parasite of Erysiphe Galeopsidis DC. on Galeopsis tetraiit L. He noted that the invading hyphae