Contributions to the Life History of A Systemic Fungous Parasite, Cryptomycina Pteridis

SUMMARY

Cryptomycina Pteridis (Rebentisch ex Fries) von Höhnel, cause of leaf-roll of bracken, was studied in its relationship to Pteridium latiusculum (Desv.) Hieron ex R. E. Fries, the eastern bracken.

1.	The fungus is systemic and perennial, overwintering in stem buds and frond buds of its host, and persisting indefinitely in a given diseased plant.
2.	The mycelium of the parasite was not found in the apical cell of the stem bud, but in the undifferentiated tissue adjacent to it, separated from it by from 2 to 11 uninvaded cells. The mycelium is both inter- and intracellular. It was occasionally seen in a bracken cell the nucleus of which was undergoing mitosis.
3.	In the maturing rhizome, which gives no external evidence of being diseased, the scattered infection areas in the various tissues remain of limited extent, and the fungus apparently dies. In the maturing frond, which exhibits striking symptoms of being diseased, the fungus spreads from originally scattered foci and develops with marked luxuriance.
4.	Typical symptoms and signs of leaf-roll disease are found only in fronds developed from diseased buds of systemically infected plants.
5.	Inoculation, with conidia, of young fronds or of immature portions of older fronds was followed by infection resulting in localized lesions.
6.	Inoculation, with conidia, of young bracken sporophytes was followed by infection resulting in systemic infection and typical leaf-roll symptoms.
7.	No systemic infection of mature plants followed the inoculation, with conidia, of (1) their fronds, or (2) the soil covering their underground parts, or (3) the underground parts themselves.
8.	No systemic infection of young sporophytes followed the inoculation, with conidia, of bracken spores or young gametophytes.
9.	Germination of conidia was obtained in various liquids and on the surface of young bracken fronds.
10.	The fungus enters the host by sending a penetration tube through the wall of an epidermal cell. The hyphae grow rapidly from cell to cell.

Specimens of material used in the above experiments and observations have been deposited in the Herbarium of the Department of Plant Pathology of Cornell University, the Farlow Herbarium of Harvard University and the Herbarium of the Bureau of Plant Industry.