Fig. 115.—An ovary with the conidial stage of Claviceps purpurea (Sphacelia).
This family may be subdivided into 3 sub-families.
Sub-Family 1. Hypocreales.
The perithecia are pale, fleshy, brightly coloured, and generally aggregated on a stroma. Conidia and chlamydospores occur very frequently. Only one order.
Order. Hypocreaceæ. In this order the majority are parasites upon Flowering-plants (Nectria, Polystigma, Epichloë, Claviceps); but some are parasites upon Fungi (Hypomyces, Melanospora), or upon insects (Cordyceps).
Fig. 116.—Claviceps purpurea. A Sclerotium with stromata (cl) (× by 2). B Stroma divided longitudinally to show the perithecia (cp). C A perithecium with the surrounding hyphæ (hy). D An ascus ruptured, with the eight filamentous ascospores emerging.
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.
Fig. 117.—Nectria cinnabarina: a branch of Acer pseudoplatanus, with conidial-layers and perithecia (nat. size); b a conidial-layer (Tuberculoria vulgaris); c, a mass of perithecia. (b and c × 8.)