. A textbook of botany for colleges and universities ... Botany. 8o MORPHOLOGY the Irichogyne. The spermatia have been found attached to the ex- posed tip of the trichogyne, with their nuclei gone; so that discharge and nuclear fusion seem to be safe in- ferences. The archi- carp then enlarges and divides, becom- ing transformed into the ascogonium, from which arise the usual ascogenoushy- phae. From hyphae beneath the asco- FlG. Tqo. — Anaplychia: section of an apothecium of a gonium the Sterile lichen, showing the hymenium made up of asci and para- branches arise that physes overlying the in
. A textbook of botany for colleges and universities ... Botany. 8o MORPHOLOGY the Irichogyne. The spermatia have been found attached to the ex- posed tip of the trichogyne, with their nuclei gone; so that discharge and nuclear fusion seem to be safe in- ferences. The archi- carp then enlarges and divides, becom- ing transformed into the ascogonium, from which arise the usual ascogenoushy- phae. From hyphae beneath the asco- FlG. Tqo. — Anaplychia: section of an apothecium of a gonium the Sterile lichen, showing the hymenium made up of asci and para- branches arise that physes overlying the inner loose mycehum of the lichen body, produce the invest- and' all invested by a thick cortical mycelium, within which . ' ., . , are apparent groups of algae. — After Sachs. ^S Sterile tissue 01 the ascocarp, the whole structure finally breaking through the surface of the thallus, usually in the form of a disklike or saucer-like ascocarp (apothecium, fig. igo). One ascocarp may involve a single ascogonium or several, just as described under Pezizales (see p. 73).. (3) Basid:omycetes This great group of fungi is characterized by the occurrence of a basidium in the life history. A basidium is the swollen end of a hypha, and consists of four cells or one cell; but in either case it usually gives rise to four slender branches (sterigmata), and each sterigma cuts off at the tip a spore (basidiospore) (fig. 201). The basidium holds the same place in the life history of a basidiomycete that an ascus does in the life history of an ascomycete. The essential feature of a basidium is that it produces spores externally and that the theoretical number of spores is four. As in the history of the ascus, the young basidium contains two nuclei which fuse. Unlike the ascus, however, the fusion nucleus of the basidium, by two successive divisions, gives rise to four nuclei, and it is these four nuclei that are found in the four spores. In some cases four sterigmata are not produced and four
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