Tar Spot Research Articles

Tar Spot of American Holly

Tar Spot of American Holly

An Early Record of the Sycamore Maple in Britain

THE sycamore maple, Acer pseudoplatanus L., is one of the hardiest of British trees, sometimes suppressing the elm by the vigour and rapidity of its growth. According to Henry1 it thrives in almost any dry soil, and seems to reach its greatest size and perfection in the colder hilly parts of England and Scotland, “where nearly all the finest specimens are found”. It is unaffected by the severest frosts, at any season, and is rarely attacked seriously by insects, or by fungi except Rhytisma acerinum (Pers.) Fries, which produces noticeable black blotches on the leaves. The sycamore maple ripens seed profusely and reproduces itself almost everywhere on clean ground, though the seedlings are easily suppressed by coarse grass. Bean2 notes that its seedlings spring up in the wilder parts of Kew Gardens in such a way that in course of time the place, if left to run wild, would probably become a sycamore forest. He points out that this is one of the few trees that will stand the full force of salt-laden winds in exposed places near the sea. Last year I found it growing on the coast of Caithness exposed to the full fury of the north wind.

Life-history and Cytology of Rhytisma acerinum (Pers.) Fries

Life-history and Cytology of Rhytisma acerinum (Pers.) Fries

Societies and Academies

LONDON. British Mycological Society, November 17.—Mr. F.T. Brooks, vice-president, in the chair.—A. A.Pearson: An account of the fungus foray of the Societe Mycologique de France.—W. J. Dowson: A mould causing a disease of sweet-pea. The mould causes a white mealy growth, in. some cases covering both sides of the leaf. No damage apparently is caused under ordinary climatic conditions, but in warm moist temperatures there is considerable effect: spots develop in ten days after infection, and produce spores in about a week. The fungus simulates a white form of Hormodendrum cladosporioides.—J.Jackson Clarke: Some mycological chromidia. A comparison of nuclear phenomena observed in Synchytrium and its allies with those of Molluscum contagium and other human diseases.—R. Paulson: Field observations on mycorrhiza. Fungus-roots occur most frequently at a depth of one to three inches below the surface of masses of decaying leaves or under moss. In the birch, most of the roots become infected within the first few weeks. The seed while still on the tree frequently has fungal hyphae between the persistent styles. These are carried down by hook-shaped processes on the hypocotyl. What part is played by this fungus (Sporotrichum) in mycorrhiza formation is as yet uncertain.—E. C. Stakman: The rust problem in America. An extempore account of the damage caused to cereals by rust, and the methods being used to overcome the disease.—A. S. Home and G. N. Jones: A new species of Eidamia. The species differs from E. acremonioides morphologically in its tuberculate macrospores and physiologically in its ability to hydrolyse starch, invert sugar, etc. The authors prove the identity of Monopodium uredopsis and E. acremonioides.—R. Bracher: Notes on Rhytisma acerinum and R. Pseudoplatani. Infection takes place from an ascospore germ tube penetrating a stoma on the lower surface. The mycelium ramifies in the palisade layer, but finally concentrates in the upper epidermal cells, subsequent development occurring in these cells and killing them, the walls being ruptured and pushed apart. Black sclerotium formation is first apparent in the thickened outer walls of the upper epidermal cells, and is later increased by the formation of an inferior plectenchymatous layer. Splitting of the apothecia is accompanied by the development of a special mechanism whereby the sclerotium is broken down by hyphal secretion in the region of the split.