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. _b._ FROM POLYTOMOUS BRANCHING. Another method of scyphus formation occurs in _Cl. amaurocrea_ and a few other species in which the branching is polytomous (several members rising from about the same level). Concrescence of the tissues at the base of these branches produces a scyphus; it is normally closed by a diaphragm that has spread out from the different bases, but frequently there is a perforation due to stretching. These species belong to the Section _Perviae_. _c._ FROM ARRESTED GROWTH. In most cases however where the scyphus is open as in _Cl. furcata_, _Cl. squamosa_, etc., development of the cup follows on cessation of growth, or on perforation at the summit of the podetium. Round this quiescent portion there rises a circle of minute prominences which carry on the apical development. As they increase in size, the spaces between them are bridged over by lateral growth, and the scyphus thus formed is large or small according to the number of these outgrowths. Apothecia or spermogonia may be produced at their tips, or the vegetative development may continue. Scyphi formed in this manner are also open or “pervious.” _d._ GONIDIA OF THE SCYPHUS. Gonidia are absent in the early stages of scyphus formation when it arises from degeneration of the apical tissues, either fertile or vegetative; but gradually they migrate from the podetium, from the base of young outgrowths, or by furrows at the edge, and so spread over the surface of the cup. Soredia may possibly alight, as Krabbe insists that they do, and may aid in colonizing the naked area. Their presence, however, would only be accidental; they are not essential, and scyphi are formed in many non-sorediate species such as _Cl. verticillata_. The cortex of the scyphus becomes in the end continuous with that of the podetium and is always similar in type.