In lecanorine development the ascending hyphae from the medulla, in some cases, carry with them algal cells which multiply and spread as a second gonidial layer under the hypothecium (Fig. 102). These hyphae may also spread in a radial direction while still within the thallus and give rise to an “immersed” apothecium which is lecanorine as it encloses gonidia within its special tissues, for example, in _Acarospora_ and _Solorina_. But in most cases the lecanorine fruit is superficial and not unfrequently it is raised on a short stalk (_Usnea_, etc.); both the primary gonidial zone of the thallus and the outer cortex are associated with the medullary column of hyphae from the first and grow up along with it, thus providing the outer part of the apothecium, an additional “thalline margin” continuous with the thallus itself. It is an advanced type of development peculiar to lichens, and it provides for fertility of long continuance which is in striking contrast with the fugitive ascocarps of the Discomycetes. [Illustration: Fig. 102. _Lecanora tartarea_ Ach. Vertical section of apothecium. _a_, hymenium; _b_, proper margin or parathecium; _c_, thalline margin or amphithecium. × 30 (after Reinke).] The distinction between lecideine and lecanorine apothecia is of great value in classification, but it is not always easily demonstrable; it is occasionally necessary to examine the early stages, as in the more advanced the thalline margin may be pushed aside by the turgid disc and become practically obliterated. The “proper margin” reaches its highest development in the lecideine and graphideine types. It is less prominent or often almost entirely replaced when the thalline margin is superadded, except in genera such as _Thelotrema_ and _Diploschistes_ which have distinct “double margins.” There is an unusual type of apothecium in the genus _Gyrophora_. The fruit is lecideine, the thalline gonidia taking no part in the development. The growth of the initial ascogenous tissue, according to Lindau[659], is constantly towards the periphery of the disc so that a weak spot arises in the centre which is promptly filled by a vigorous sterile growth of paraphyses. This process is repeated from new centres again and again, resulting in the irregularly concentric lines of sterile and fertile areas of the “gyrose” fruit (Fig. 103). The paraphyses soon become black at the tips. Asci are not formed until the ascogenous layer has acquired a certain degree of stability, and spores are accordingly present only in advanced stages of growth. [Illustration: Fig. 103. Apothecial gyrose discs of _Gyrophora cylindrica_ Ach. × 12 (after Lindau).] G. LICHEN ASCI AND SPORES