The order Glyphidei has no true excipulum; the coloured discs are at first immersed in the medullary stratum of a crustaceous thallus, the crust then rises into distinct expansions, in the centre of which the coloured discs are set like gems in a mosaic. ‘There is in fact no true border to the disc, the perithecium being reduced to a thick conical base, from which proceed immediately the asci and paraphyses; each individual hymenium being surrounded by the intervening medullary matter injected, as it were, into the interstices.’ The whole surface of Chiodecton monostichum is productive, and in that genus M. Tulasne found vessels in the form of little scattered perithecia, containing filiform curved fertilizing particles. The species of this order are almost wholly tropical, though the Chiodecton myrticola has been found in Ireland. The order Caliciei consists of horizontal lichens, with generally an ill-developed crust; the discs, which are at first covered by a veil, are contained in a stalked, or more rarely sessile, excipulum, looking like little flat-headed pins stuck into the crust; the veil at length vanishes, and exposes a pulverulent mass of spores, which adhere so loosely in the Calicium inquinans, that they soil the finger if touched; in other cases they come out of their ascus like little necklaces. The species of these lichens are almost entirely confined to Europe and North America. In the second division of Lichenaceæ, the ANGIOCARPEI, the discs are enclosed in an excipulum, which projects from the surface of the plant, and ultimately discharges the spores from a rupture or pore in its surface. Besides the fructification consisting of perithecia containing paraphyses and asci with their enclosed sporidia, there is a nucleus in each disc, either of firm or deliquescent matter. Some of the lichens of this group are parasitic, others are aquatic. The order Limboriei, like parasitic fungi, begin their existence under the thick skin of the leaves of tropical plants, spread their crustaceous thallus over their surface, and destroy their beauty, by stopping up their pores, and preventing the admission of light to their tissues. The excipulum and perithecia are black, and the latter burst in an irregular fissure, and are in most cases covered by a beautifully sculptured crust. The crustaceous fronds of the Verrucariei are often so thin as to be inseparable from the substance over which they spread. The excipula are closed, the walls of the perithecia are often black, and in some species more or less crowded round a columella. In the Verrucaria muralis fertilizing particles have been discovered. The plants are widely distributed, and at least one species spreads its crust over the smooth stones in running streams.