Part 25

The most important member of this order is the ERGOT (Claviceps purpurea, Figs. 114, 115, 116). This Fungus is found in the flowers of many species of Grasses, especially the Rye, attacking and destroying the ovaries. In the FIRST or CONIDIAL STAGE of the attack, the ovaries are found covered with a white, irregularly folded mycelium (Fig. 114 m, Fig. 115), formed of numerous hyphæ woven together and penetrating the wall of the ovary. From these a number of hyphæ (Fig. 114 a) project into the air and abstrict from their apices the conidia (b) which serve as reproductive organs. The mycelium also secretes a sticky, stinking fluid (honey-dew) in which the conidia are embedded in great numbers. The honey-dew exudes from the bases of the glumes, and is greedily sought by flies, which thus carry the conidia to other ovaries. In this manner fresh ears are infected, which might escape were the conidia only distributed by the wind. This stage formerly was regarded as an independent Fungus, known as Sphacelia segetum (Fig. 115). On germination, the conidia produce either a new mycelium (Fig. 114 d, c), or new conidia. The SECOND or SCLEROTIUM STAGE is the one in which the Fungus passes the winter. The mycelium penetrates deeper and deeper into the attacked ovaries, their tissues are destroyed and replaced by the hyphæ, which gradually become more and more felted together. A firm, pseudo-parenchymatous mass of hyphæ is thus formed at the base of the loosely-woven Sphacelia, which is in part transformed into the hard sclerotium, and the remainder thrown off. A dark, hard, poisonous body, longer than the natural grain, is thus formed; these bodies are known as Ergots, and were formerly considered to be a distinct species,--Sclerotium clavus (“Secale cornutum,” Ergot, Fig. 116 A, c). The THIRD STAGE, described as Claviceps purpurea, is developed in the following spring from the germinating sclerotium, which produces dark-red stromata with short stalks. In the stroma numerous perithecia with asci and ascospores are produced. The latter may infect young flowers of the cereals, in which the disease is then developed as before.

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.

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.

Order 1. =Sordariaceæ.=--Fungi living on dung with fragile perithecia, either aerial or buried in the substratum. The dark brown or black spores have either a mucilaginous envelope (Sordaria, etc.) or mucilaginous appendages (Podospora), by means of which their expulsion and distribution are promoted.

Order 2. =Chætomiaceæ.= Perithecia fragile, free, bearing on the summit a tuft of hairs. Chætomium, on decaying vegetable matter.

Orders 3–7. Perithecia scattered or aggregated, situated from the commencement on the surface of the substratum. Stroma wanting.

Order 3. =Trichosphæriaceæ.= Trichosphæria parasitica (Fig. 121), on Abies alba; Herpotrichia nigra on Picea excelsa and Pinus montana.

Order 4. =Melanommaceæ.= Rosellinia quercina lives in the roots of 1–3-year-old Oaks, and destroys the plants.

Order 5. =Ceratostomaceæ.=

Order 6. =Amphisphæriaceæ.= Strickeria obducens (Fig. 120) has brick-like spores, and lives aggregated on the hard branches of Fraxinus.

Order 7. =Lophiostomaceæ.=

Order 8. =Cucurbitariaceæ.= Perithecia tufted, at first embedded, then breaking through, often situated upon an indistinct stroma.

Orders 9–13. The perithecia remain embedded, and are only liberated by the casting off of the covering layers of the substratum. Stroma wanting.

Order 9. =Sphærellaceæ.= The species of Sphærella have colourless, bicellular spores. They live upon the leaves of many plants, and develope spherical perithecia upon the fallen leaves.

Order 10. =Pleosporaceæ.= The conidial-forms of Pleospora herbarum and P. vulgaris form a black covering on various plants, known as “smuts.”--Venturia ditricha occurs on the underside of dry Birch leaves, and perhaps to this belongs the conidial-form, Fusicladium pirinum, which causes the “Rust spots” on Apples and Pears.

Order 11. =Massariaceæ.=

Order 12. =Clypeosphæriaceæ.=

Order 13. =Gnomoniaceæ.= Perithecia, with peak-like aperture. Gnomonia erythrostoma in the leaves of Prunus avium, which turn brown and do not fall in autumn.

Orders 14–18. Stroma generally well developed. The perithecia are embedded in the stroma, but when this is rudimentary, in the substratum.

Order 14. =Valsaceæ.= Valsa.

Order 15. =Diatrypaceæ.= Diatrype.

Order 16. =Melanconidaceæ.=

Order 17. =Melogrammataceæ.=

Order 18. =Xylariaceæ.= This order is the most highly developed of the Sphæriales. The stroma arises on the surface of the substratum, which is generally dead or decorticated wood; it is well-developed, crustaceous, hemispherical or upright. In the younger conditions it is covered with a layer of conidia, and later on it bears the perithecia, arranged in a layer immediately beneath its surface. The ascospores are of a dark colour. Often also there are free conidiophores.

Hypoxylon and Ustulina have a cushion-like or crustaceous stroma.--Xylaria has a club-shaped or branched stroma, often several centimetres high. X. hypoxylon (Fig. 122) and X. polymorpha occur on old tree stumps.--Poronia grows on old horse dung, and has a conical stroma.

Sub-Family 3. =Dothideales.=