Fig. 144.—Cladonia pyxidata.
Sub-Class 2. Basidiomycetes.
This sub-class embraces the most highly developed Fungi, with large “fruit-bodies,” which in ordinary language we shortly term Funguses, Toadstools, or Mushrooms.
They have no sporangia, but reproduce only by means of basidiospores, conidia, chlamydospores and oidia. The chief characteristic of this sub-class is the basidium (Fig. [145]), i.e. the conidiophore, which has a distinctive form, and bears a definite number (generally 4) of characteristically shaped conidia (basidiospores, Fig. [145] c, d, e).
Fig. 145.—Development of spores in Corticium.
The summit of each basidium is produced generally into four conical points (sterigmata, Fig. [145] b), from each of which a basidiospore is abstricted. The basidia may be classified into three principal groups, each of which accompanies a distinctive conidiophore: 1, the long, filamentous, transversely divided basidia, with lateral sterigmata and spores, found in the Uredinaceæ (Figs. [146] D, [153]), Auriculariaceæ (Fig. [160] B), and Pilacraceæ; 2, the spherical, longitudinally divided basidia of the Tremellaceæ (Figs. [160] C d; [161] iii. iv.); and 3, the ovoid, or cylindrical, undivided basidia of the Autobasidiomycetes (Figs. [145], [163], etc.); the two last have apical sterigmata and spores.
The first two groups are the septate basidia (protobasidia), of the Protobasidiomycetes; while the unseptate basidia (autobasidia) of the Autobasidiomycetes are the third group. On the formation of the basidiospores, the nucleus of the basidium divides into four nuclei, each of which is transferred to a spore.
In addition to the basidia, simple conidiophores are also found. In the Protobasidiomycetes, the simple conidia are very generally found as accessory methods of reproduction in conjunction with the basidiospores; but less frequently in the Autobasidiomycetes, e.g. among the Dacryomycetes, Tomentellaceæ, Heterobasidion annosum.