The three last named types of sporophores represent Nylander’s section of arthrosterigmata. Steiner has followed Nylander in also arranging the various forms into two leading groups. The first, characterized by the secondary branch or “sterigma,” he designates “exobasidial”; the second, comprising the three last types in which the spores are borne directly on the cells of the sporophore or on very short processes, he describes as “endobasidial.” Steiner also introduces a new term, fulcrum, for the sporophore.
The pycnidia in which these different sporophores occur are not, as a rule, characteristic of one family. Peltigera type is found only in one family and the Cladonia type is fairly constant in Cladoniae, but “Psora” pycnidia are found on very varying lichens among the Lecideaceae, Verrucariaceae and others. The Squamaria type with long bent spores is found not only in Squamaria (Glück’s Placodium) but also in Lecidea, Roccella, Pyrenula, etc. Parmelia type is characteristic of many Parmeliae and also of species of Evernia, Alectoria, Platysma and Cetraria. The Sticta type occurs in Gyrophora, Umbilicaria, Nephromium and Lecanora as well as in Sticta and in one species at least of Collema. To the Physcia type belong the pycnidia of most Physciaceae and of various Parmeliae, and to the closely related Endocarpon type the pycnidia of Endocarpon and of Xanthoria parietina.
Fig. 114. Sterile filaments in spermogonia of Lecidea fuscoatra Ach. much magnified (after Lindsay).
c. Periphyses and Sterile Filaments. In a few species, Roccella tinctoria, Pertusaria globulifera, etc., short one-celled sterile hyphae are formed within the spermogonium near the ostiole, towards which they converge. They correspond to the periphyses in the perithecia of some Pyrenolichens, Verrucaria, etc. (described by Gibelli[720] as spermatiophores); they are also present in some of the Pyrenomycetes (Sordaria, etc.), and in many cases replace the paraphyses in function when these have broken down. Sterile hyphae also occur, towards the base, mingled with the fertile spermatiophores ([Fig. 114]). These latter were first described and figured by Tulasne[721] in the spermogonia of Ramalina fraxinea as stoutish branching filaments, rising from the same base as the spermatiophores but much longer, and frequently anastomosing with each other. They have been noted also in Usnea barbata and in several species of Parmelia, and have been compared by Nylander[722] to paraphyses. They are usually colourless, but, in the Parmeliae, are often brownish and thus easily distinguished from the spermatiophores. It has been stated that these filaments are sometimes fertile. Similar sterile hyphae have been recorded in the pycnidia of fungi, in Sporocladus (Hendersonia) lichenicola (Sphaeropsideae) by Corda[723] who described them as paraphyses, and also in Steganosporium cellulosum (Melanconieae). These observations have been confirmed by Allescher[724] in his recent work on Fungi Imperfecti. Keiszler[725] has described a Phoma-like, pycnidium parasitic on the leprose thallus of Haematomma elatinum. It contains short slender sporophores and, mixed with these, long branched sterile hyphae which reach to the ostiole and evidently function as paraphyses, though Keiszler suggests that they may be a second form of sporophore that has become sterile. On account of their presence he placed the fungus in a new genus Lichenophoma.
E. Spermatia or Pycnidiospores
a. Origin and Form of Spermatia. Lichen spermatia arise at the tips of the sterigmata either through simple abstriction or by budding. In the former case—as in the Squamaria type—a delicate cross-wall is formed by which the spermatium is separated off. When they arise by budding, there is first a small clavate sac-like swelling of the end of the short process or sterigma which gradually grows out into a spermatium on a very narrow base. This latter formation occurs in the Sticta, Physcia and Endocarpon types.
Nylander[726] has distinguished the following forms of spermatia:
1. Ob-clavate, the broad end attached to the sterigma as in Usneae, Cetraria glauca and C. juniperina.
2. Acicular and minute but slightly swollen at each end, somewhat dumb-bell like, in Cetraria nivalis, C. cucullata, Alectoria, Evernia and some Parmeliae, frequently borne on “arthrosterigmata.”