C. Development of the Scyphus
Two types of podetia occur in Cladonia: those that end abruptly and are crowned when fertile by the apothecia or spermogonia (pycnidia), or if sterile grow indefinitely tapering gradually to a point ([Fig. 70]); and those that widen out into the trumpet-shaped or cup-like expansion called the scyphus ([Fig. 69]). Species may be constantly scyphiferous or as constantly ascyphous; in a few species, and even in individual tufts, both types of podetium may be present.
Fig. 70. Cladonia furcata Schrad. Sterile thallus (S.H., Photo.).
Wainio[398], who has studied every stage of development in the Cladoniae, has described the scyphus as originating in several different ways:
a. From abortive Apothecia. In certain species the apothecium appears at a very early stage in the development of the podetium of which it occupies the apical region. Owing to the subsequent formation of the tubular cavity in the centre of the stalk, the base of the apothecium may eventually lie directly over the hollow space and, therefore, out of touch with the growing assimilating tissues; or even before the appearance of the tube, the wide separation between the primordium of the apothecium and the gonidia, entailing deficient nutrition, may have produced a similar effect. In either case central degeneration of the apothecium sets in, and the hypothecial filaments, having begun to grow radially, continue to travel in the same direction both outwards and upwards so that gradually a cup-shaped structure is evolved—the amphithecium of the fruit without the thecium.
The whole or only a part of the apothecium may be abortive, and the scyphus may therefore be entirely sterile or the fruits may survive at the edges. The apothecia may even be entirely abortive after a fertile commencement, but in that case also the primordial hyphae retain the primitive impulse not only to radial direction, but also to the more copious branching, and a scyphus is formed as in the previous case. It must also be borne in mind that the tendency in many Cladonia species to scyphiform has become hereditary.
Baur[399], in his study of Cl. pyxidata, has taken the view that the origin of the scyphus was due to a stronger apical growth of the hyphae at the circumference than over the central tubular portion of the podetium, and that considerable intercalary growth added to the expanding sides of the cup.
Scyphi originating from an abortive apothecium are characteristic of species in which the base is closed (Wainio’s Section Clausae), the tissue in that case being continuous over the inside of the cup as in Cl. pyxidata, Cl. coccifera and many others.