Several species of the genus Nectria, with blood-red perithecia, are found as dangerous parasites, especially N. ditissima, which causes “Canker” in the Beech, Ash, and Apple, etc.; N. cucurbitula, which appears on Pine-trees, and N. cinnabarina (Fig. [117]), whose conidial form was formerly named Tubercularia vulgaris.—Polystigma rubrum forms shining red spots on the green leaves of Prunus-species.—Epichloë typhina is parasitic on the sheaths of Grasses, on which it first forms a white conidial-layer, later on a yellow layer of perithecia.—Cordyceps (Chrysalis Fungus, Figs. [118], [119]) lives in and destroys insects, and after compassing their death produces the club-formed, generally yellow, stromata, one part of which bears conidia (Isaria) and another perithecia. C. militaris (Fig. [118]) on the chrysalides and caterpillars of moths, is the most common.
The so-called Botrytis bassiana, which produces the disease known by the name of “Muscardine,” in silkworms, is probably a conidial form belonging to Cordyceps.
Fig. 118.—Cordyceps militaris. I Stromata with conidiophores (Isaria farinosa). II A larva, with stromata, bearing perithecia. III A spore.
Fig. 119.—Cordyceps robertii on the larva of Hepialus virescens: a stalk of stroma; b perithecia.
Sub-Family 2. Sphæriales.
To this sub-family belong the majority of the Pyrenomycetes. The perithecia are of a firm consistence (tough, leathery, woody or carbonaceous), and of a dark colour. Their covering is quite distinct from the stroma when this structure is present. The stromata are sometimes very large, and may be either cushion-like, crustaceous, upright and club-like, or branched bodies. In general, small, inconspicuous Fungi, living on dead vegetable matter, sometimes parasites. Free conidiophores and conidiocarps are known in many species, and in several, chlamydospore-like forms of reproduction. Orders 3–18 constitute the Sphæriaceæ of older systematists.
Fig. 120.—Strickeria obducens: a a portion of an Ash-branch with the bark partly thrown off; on the wood are numerous black perithecia (× 20); b longitudinal section through a perithecium; c a spore; d longitudinal section through a pycnidium whose ascospores are being ejected; e portion of the same, with hyphæ and spores.