Order 4. =Nidulariaceæ= (=Nest-Fungi=). Small Fungi of which the fruit-body at first is spherical or cylindrical but upon maturity it becomes cupular or vase-like, and contains several lenticular “peridiola” lying like eggs in a nest. The peridiola are the chambers which contain the hymenium, covered by a thin layer of the gleba, all the remaining portion of the gleba becoming dissolved. On decaying wood. _Nidularia_ has spherical fruit-bodies containing a large number of lenticular peridiola, embedded in a slimy mass.--_Crucibulum_ has fruit-bodies resembling crucibles with discoid peridiola, each with a spirally-twisted stalk.--_Cyathus_ has a fruit-body, which when open is campanulate, with stratified peridium, and long-stalked, lense-shaped peridiola. Order 5. =Hymenogastraceæ.= Fruit-bodies tubercular, globose and subterranean, resembling very closely the Truffles, from which they can only be distinguished with certainty by microscopic means. The peridium is simple, capillitium wanting, and the gleba encloses a system of labyrinthine passages covered with a continuous hymenium. The fruit-bodies persist for some time, and form a fleshy mass, the spores being only set free by the decay of the fruit-body, or when it is eaten by animals. The majority are South European. _Hymenogaster_, _Melanogaster_, _Rhizopogon_ (Fig. 181 I-IV). APPENDIX TO THE BASIDIOMYCETES: Basidiolichenes (Lichen-forming Basidiomycetes). Several Fungi belonging to the Basidiomycetes have a symbiotic relationship with Algæ exactly similar to that enjoyed by certain Ascomycetes, and these are therefore included under the term Lichens (p. 136). They are chiefly tropical. Order 1. =Hymenolichenes.= To this order belong some gymnocarpic forms: _Cora_, _Dictyonema_, _Laudatea_.[15] Order 2. =Gasterolichenes.= To this belong some angiocarpic forms: _Emericella_, _Trichocoma_. APPENDIX TO THE FUNGI. Fungi imperfecti (Incompletely known Fungi). 1. The =Saccharomyces-forms= are Fungi which are only known in their yeast-conidial form. They are _conidia of higher Fungi_ which can multiply to an unlimited extent by budding in nutritive solutions, and in this way maintain their _definite_ size and shape. The budding takes place _only at the ends_ of the conidia. The wall of the conidium forms at one or at both ends a small wart-like outgrowth, which gradually becomes larger, and is finally separated from its mother-cell as an independent cell, surrounded by a closed cell-wall (Fig. 182 _a_, _b_). [Illustration: FIG. 182.--Beer-yeast (_Saccharomyces cerevisiæ_): _a-b_ (× 400); _c-f_ (× 750); _c_ a cell in the process of forming spores; _d_ a cell with four ripe spores; _e_ the spores liberated by the dissolution of the cell-wall; _f_ three germinating spores; _g_ mycelium-like cell-chains. (× 1000: after Em. Chr. Hansen.)]