PERONOSPOREI, De By.
Peronospora, Casp.
Parasitic threads mostly inarticulate. Spores of two kinds:—1. Acrospores on the tips of the branchlets; 2. Oospores large, globose, on the creeping mycelium.
Peronospora infestans, Mont. Potato Mould; threads of mycelium slender, always destitute of suckers; fertile threads thin, gradually attenuated upwards, with one to five branches, one or more inflated vesicles near the apices of the branches; branches either simple or with short branchlets; acrospores ellipsoid or ovoid; apex furnished with a prominent papilla.—On leaves, stems, and tubers of the Potato, causing the potato-murrain. Very common since 1845. ([Plate XIV.] fig. 264.)
Peronospora nivea, Ung. (P. macrospora, B.). Parsnip Mould; threads of mycelium stout, often torulose; suckers numerous, vesicular, obovate; fertile threads fasciculate, dwarfish, tapering or subulate, or once or twice shortly bifurcate, rarely trifurcate, with one to four horizontal branches near the summit, once, twice, or three times bifurcate; acrospores subglobose or ovoid, with an obtuse papilla at the apex.—On various Umbelliferæ. Common and variable.
Peronospora pygmæa, Ung. (P. curta, Berk.). Anemone Mould; threads of mycelium thickened, often constricted and varicose; suckers minute, obovate, or pear-shaped; fertile threads fasciculate (2-5 or more), simple above or divided at the apex into 2-4 short simple branches, or shortly twice dichotomous, or all simple, obtuse, surmounted by 2-4 short spicules; acrospores ovoid or ellipsoid, variable in size; apices broadly and obtusely papillate.—On Wood-anemone. Not uncommon. ([Plate XV.] fig. 267.)
Peronospora gangliformis, Berk. Lettuce Mould; threads of the mycelium stout, now and then torulose; suckers vesicular, obovate or clavate; fertile threads 2-6 times dichotomous, sometimes trichotomous; stems and primary branches slender, dilated or inflated above; the ultimate ramuli inflated at the apex into a turbinate or subglobose vesicle bearing from 2-8 subulate processes or spicules; acrospores minute, subglobose; apices with broad depressed papillæ, produced on the spicular processes, On Lettuces and other Compositæ. Frequent. ([Plate XIV.] fig. 265.)
Peronospora parasitica, Pers. Cabbage Mould; threads of the mycelium thickened and much branched; suckers numerous, branched; branches clavate, obtuse; fertile threads thick, soft, flexile, equal or unequal, 5-8 times dichotomous, rarely trichotomous; branches always repeatedly trifurcate; acrospores broadly elliptical, very obtuse at the apex, white.—On Cabbages, Shepherd’s-purse, and other Cruciferæ, sometimes in company with Cystopus candidus. Summer and autumn. Common. ([Plate XIII.] fig. 262.)
Peronospora Viciæ, Berk. Pea Mould; fertile threads densely cæspitose, erect, equal, rarely unequal, 6-7-8 times dichotomous; ultimate ramuli shortly subulate, acute; acrospores ellipsoid, very obtuse at the apex, obtuse or slightly acute at the base; membrane with a violaceous tint.—On Tares, Peas, &c. Frequent. ([Plate XV.] fig. 266; [Plate X.] fig. 212.)
Peronospora Arenariæ, Berk. Sandwort Mould; fertile threads slender, 6-7 times equally, rarely unequally, dichotomous; branches spreading; ultimate ramuli slender, acute, subulate, nearly erect; acrospores broadly elliptical, oftentimes very obtuse, small; membrane scarcely violaceous.—On Arenaria serpyllifolia and A. trinervis.—June. ([Plate XVI.] fig. 268; [Plate X.] fig. 211.)
Peronospora effusa, Grev. Spinach Mould; fertile threads fasciculate, short, thick, 2-6, rarely 7 times dichotomous above; acrospores broadly ellipsoid, sometimes very obtuse; membrane with a violaceous tint. On Spinach, Goosefoot, and some other allied plants. Spring and autumn. Not uncommon. ([Plate X.] figs. 214, 215.)
Peronospora Urticæ, Casp. Nettle Mould; fertile threads small, loosely 4-6 times dichotomous; branches flexuose, ultimate ramuli subulate, arcuate, often deflexed; acrospores large, broadly ovoid or subglobose, distinctly pedicellate; apices very obtuse; membrane violaceous.—On leaves of the common Nettle.
Peronospora trifoliorum, De By. Clover Mould; fertile threads cæspitose, equally or unequally 6-7 times dichotomous, rarely trichotomous; ultimate branches subulate, acute, slightly curved; acrospores ellipsoid, very obtuse; membrane with a slightly violaceous tint; oospores large; epispore brown.—On Lucern (Medicago sativa). Highgate and Hampstead, 1864.
Peronospora grisea, Ung. Veronica Mould; fertile threads erect, fasciculate, grey, 5-7 times regularly dichotomous; branches gradually attenuated; primary oblique erect; others spreading, flexuose; ultimate mostly unequal, slightly arcuate; acrospores ellipsoid or ovoid, obtuse; membrane pale and dirty violet.—On leaves of Veronica beccabunga. May, 1846. ([Plate X.] fig. 213.)
Peronospora arborescens, Berk. Poppy Mould; fertile threads slender, erect, 7-10 times dichotomous above; branches more or less flexuose, squarrose, spreading, gradually attenuated; ultimate ramuli shortly subulate, more or less arcuate; acrospores very small, subglobose; membrane scarcely violaceous.—On the Corn Poppy. June. Common.
Peronospora Schleideniana, De By. (P. Destructor, B.) Onion Mould; fertile threads robust, erect, not septate, branched alternately; ultimate ramuli forked and uncinate or divaricate; acrospores seated on the tips of the ultimate ramuli, obovoid or nearly pear-shaped, attenuated at the base; membrane of a dirty violet-colour.—On the leaves of various species of Allium. Often plentiful. ([Plate XIII.] fig. 263.)
Peronospora violacea, Berk. Scabious Mould; fertile threads branched; acrospores sub-elliptical, violet-coloured. All that is known of this species is contained in the following note from the Rev. M. J. Berkeley:—“It grew on the petals of the common scabious. I have not found it again, and have either lost or mislaid my specimens. You may describe it as læte violacea; floccis ramosis; sporis subellipticis, violaceis. It is probably the Farinaria on Scabious of Sowerby.” (M. J. B.)
Peronospora sordida, Berk. Figwort Mould; forming broad, irregular, dirty, pallid spots on the under surface of the leaves; fertile threads loosely dichotomous above; tips forked, unequal; acrospores obovate, apiculate.—On leaves of Scrophularia. Jedburgh.
Peronospora sparsa, Berk. Rose Mould; fertile threads scattered, by no means torulose, ultimate branches scarcely uncinate, dichotomous, pallid grey; acrospores sub-elliptical.—On the under side of rose-leaves in conservatories.
Peronospora obliqua, Cooke. Dock Mould; threads of the mycelium slender; fertile threads fasciculate, erect, simple, rarely bifurcate, attenuated upwards; acrospores large, ellipsoid, attached obliquely near the base.—On the under surface of dock leaves. Winter and spring. Probably not uncommon. Brownish circular spots on the leaves indicate the presence of this mould, which is so minute that it might otherwise be overlooked. ([Plate XVI.] fig. 269.)
Erysiphei.
Conceptacle with one sporangium.
Appendages floccose Sphærotheca.
Conceptacle with many sporangia.
Appendages needle-shaped, rigid Phyllactinia.
Appendages hooked Uncinula.
Appendages dichotomous Microsphæria.
Appendages floccose Erysiphe.
Sphærotheca, Lév.
Mycelium arachnoid; perithecia globose, containing a single globose sporangium; appendages numerous, floccose.—Berk. Outl., p. 404.
Sphærotheca pannosa, Lév. Rose Blight; mycelium thickened, woolly, felted, persistent; conceptacles minute, globose, scattered; appendages floccose, white; sporangium many-spored.—On the branches, calyces, petioles, and leaves of Roses. Very common. ([Plate XI.] figs. 217, 218.)
Sphærotheca Castagnei, Lév. Hop Blight; on both surfaces; mycelium effuse, web-like, commonly evanescent; conceptacles minute, scattered, globose; appendages numerous, short, flexuose above; sporangium many-spored.—On the leaves of the Hop, Meadow-sweet, and various other plants. Common. ([Plate XI.] fig. 216.)
Phyllactinia, Lév.
Perithecia hemispherical, at length depressed, seated on a persistent or evanescent membranaceo-granular receptacle; appendages straight, rigid, acicular, at length bent back.—Berk. Outl., p. 404.
Phyllactinia guttata, Lév. Hazel Blight; amphigenous; mycelium web-like, often evanescent; conceptacles large, scattered, hemispherical, at length depressed; appendages hyaline, rigid, simple; sporangia 4-20, containing 2-4 spores.—On the leaves of Hawthorn, Hazel, Ash, Elm, Alder, Beech, Birch, Oak, Hornbeam, and various other plants. Common. ([Plate XI.] figs. 219, 220.)
Uncinula, Lév.
Mycelium floccose; perithecia globose; appendages rigid, simple, bifid or dichotomous, uncinate, at length bent upwards.—Berk. Outl., p. 404.
Uncinula adunca, Lév. Willow Blight; mycelium variable; conceptacles scattered or gregarious, minute; appendages simple; sporangia 8-12, sub-pyriform, containing 4 spores.—On the leaves of Willows, Poplars, Birch, &c. Not uncommon. ([Plate XI.] figs. 221-224.)
Uncinula bicornis, Lév. Maple Blight; amphigenous; mycelium web-like, effuse, evanescent, or like a membrane and persistent; conceptacles large, hemispherical, at length depressed; appendages simple, bifid or dichotomous, uncinate; sporangia 8, sub-pyriform, containing 8 spores.—On the leaves of Maples. Common. ([Plate XI.] figs. 225-228.)
Microsphæria, Lév.
Mycelium arachnoid; appendages straight, dichotomous; branchlets swelling at the tip, or filiform.—Berk. Outl., p. 404.
Microsphæria Hedwigii, Lév. Mealy Guelder-rose Blight; hypophyllous; mycelium web-like, evanescent; conceptacles minute, globose, scattered; appendages few, very little longer than the diameter of the conceptacles; sporangia 4, ovate, containing 4 spores.—On leaves of mealy Guelder-rose. Near Greenhithe, Kent.
Microsphæria penicillata, Lév. Guelder-rose Blight; amphigenous; mycelium web-like, effuse, evanescent; conceptacles scattered, minute, globose; appendages 8-12, equal to the diameter of the conceptacle; sporangia 4, ovate, rostrate, containing 8 spores.—On leaves of Guelder-rose and Alder. Probably not uncommon. ([Plate XI.] fig. 234.)
Microsphæria Mougeotii, Lév. Tea-tree Blight; amphigenous; mycelium web-like, oftentimes persistent; conceptacles minute, scattered or gregarious, globose, at length depressed; appendages loosely dichotomous; sporangia 12-16, on a short pedicel, 2-spored.—On leaves of Lycium barbarum. Near Dartford, Kent. October, 1864.
Microsphæria Berberidis, Lév. Berberry Blight; amphigenous; mycelium web-like, oftentimes persistent; conceptacles scattered or gregarious, globose, minute; appendages few (5-10); branchlets long, divaricate, obtuse at their apices; sporangia 6, ovate, containing 6-8 spores.—On leaves of the common Berberry. Autumn. Frequent. ([Plate XI.] figs. 229-232.)
Microsphæria grossulariæ, Lév. Gooseberry Blight; amphigenous; mycelium web-like, fugacious or persistent; conceptacles scattered or gregarious, globose, minute; appendages 10-15, vaguely dichotomous, ultimate branchlets bidentate; sporangia 4-8, ovate, containing 4-5 spores.—On Gooseberry-leaves. Autumn. Frequent.
Erysiphe, Hedw.
Mycelium arachnoid; appendages floccose, simple or irregularly branched.—Berk. Outl., p. 404.
* Sporangia 2-spored.
Erysiphe Linkii, Lév. Mugwort Blight; amphigenous; mycelium web-like; fugacious or persistent; conceptacles minute, globose, scattered, emersed; appendages white, interwoven with the mycelium; sporangia 8-20, pyriform, with elongated pedicels.—On leaves of Mugwort. Autumn. Frequent. ([Plate XII.] figs. 248, 249.)
Erysiphe lamprocarpa, Lév. Composite Blight; amphigenous; mycelium web-like, fugacious or persistent; conceptacles minute, globose, scattered, or gregarious; appendages coloured, interwoven with the mycelium; sporangia 8-16, shortly pedicellate.—On leaves of Salsify, Scorzonera, Plantain, &c. Autumn. Not uncommon. ([Plate XII.] figs. 250, 251.)
** Sporangia 3-8-spored.
Erysiphe graminis, D.C. Grass Blight; amphigenous or epiphyllous; mycelium effuse, floccose, persistent; conceptacles large, gregarious or disseminated, hemispherical, at length depressed and semi-immersed; appendages simple or interwoven with the mycelium; sporangia 20-24, ovate, pedicellate, with 8 spores.—On leaves of Grasses. Autumn. Frequent. ([Plate XI.] figs. 235, 236.)
Erysiphe Martii, Lk. Pea Blight; amphigenous; mycelium web-like, very often evanescent, globose; appendages short, interwoven with the mycelium; sporangia 4-8, globose, pedicellate, with 4-8 spores.—On leaves of Peas, Beans, Umbelliferæ, and other plants. Autumn. Very common. ([Plate XI.] figs. 237-239.)
Erysiphe Montagnei, Lév. Burdock Blight; amphigenous or hypophyllous; mycelium web-like, evanescent; conceptacles minute, globose, gregarious or scattered; appendages distinct from the mycelium; sporangia 8, ovate, rostrate, with 2-3 spores.—On leaves of Burdock. Not uncommon.
Erysiphe tortilis, Lk. Cornel Blight; hypophyllous; mycelium web-like, effuse, evanescent; conceptacles minute, globose; appendages ten times as long, free from the mycelium, flexuose; sporangia 4, ovate, rostrate, with 4 spores.—On leaves of the common Dogwood. Autumn. Frequent. ([Plate XII.] figs. 245, 246.)
Erysiphe communis, Schl. Buttercup Blight; hypophyllous; mycelium effuse, web-like, evanescent or persistent; conceptacles minute, globose, scattered or gregarious; appendages short; sporangia 4-8, ovate, rostrate, with 4-8 spores.—On leaves of various Ranunculaceæ, Leguminosæ, and other plants. Autumn. Very common. ([Plate XI.] figs. 240-242.)
Chætomium, Kze.
Perithecium thin, brittle, mouthless; sporangia linear, containing dark lemon-shaped spores. Berk. Outl., p. 405.
Chætomium elatum, Kze. Straw-bristle Mould; perithecium sub-ovate, base radiato-fibrose, hairs of the vertex very long, interwoven, branched; spores broadly elliptic, apiculate at either end.—On mouldering straw, reeds, matting, &c. Very common. ([Plate XII.] figs. 257-259.)
Chætomium chartarum, Ehb. Paper-bristle Mould; perithecium subglobose, black, surrounded by a bright yellow spot; spores subglobose.—On paper. Stibbington, Hants. Rare. ([Plate XII.] figs. 252, 253.)
Chætomium glabrum, B. This species has never been described. It was recorded, by name only, in Berkeley’s Outlines, and, the specimens being mislaid, that gentleman is unable to describe it completely and correctly. “It grew abundantly on straw, and differed from Chætomium elatum in being perfectly free from hairs.”—(M. J. B.)—On damp straw.
Ascotricha, Berk.
Perithecium thin, free, mouthless, seated on loose, branched, conidiiferous threads; sporangia linear, containing dark elliptic spores.—Berk. Outl., p. 405.
Ascotricha chartarum, B. Paper Mildew; perithecium thin, olive-brown, seated on radiating flocci; sporangia linear, numerous; spores broadly elliptic, chocolate-coloured.—On white printed paper in a deal candle-box. King’s Cliffe. ([Plate XII.] figs. 254-256.)
Eurotium, Link.
Perithecia reticulated, vesicular, coloured, attached to mucedinous threads; sporangia delicate.—Berk. Outl., p. 405.
Eurotium herbariorum, Lk. Herbarium Mould; perithecium spherical, sub-depressed, yellow, seated upon radiating expanded, branched, intricate flocci.—On plants in herbaria, and various decaying substances. Very common. ([Plate XII.] figs. 260, 261.)