Order 4. =Ascobolaceæ.= Apothecia fleshy; in the later stages flat or convex. The asci are, comparatively speaking, large, and often contain a great number of spores which escape by the casting off of a lid on the summit of the ascus. Generally living on dung.--_Ascobolus furfuraceus_, etc. Family 6. =Helvellales.= These Fungi have the appearance of clubs, bells, or mushrooms, consisting of an upright _stalk_ bearing a _large and fleshy_ head, on the _exterior surface_ of which the _hymenium_ is spread. The ascocarps are probably gymnocarpic from the beginning, and on this account these plants are placed in a separate family. The development of the ascocarps is unknown. The _Morchella_ (Morell) grows on the ground; some species are edible. 1 order. Order. =Helvellaceæ.= _Spathulea_ is yellow and club-shaped, and forms “fairy rings” in woods.--_Geoglossum_ (Earth-tongue) projects above the ground as a black tongue, or as a club-shaped body. Several species are found in meadows and on heaths.--_Helvella_ has a stalk, bearing an irregularly folded head, on the external surface of which is the hypothecium.--_Morchella_ (Morell, Fig. 130), the stalk bears on its summit the conical or spherical head, the external surface of which is reticulate and bears the asci.--_Mitrula. Verpa._ [Illustration: FIG. 130.--_Morchella esculenta_: _a_ an entire specimen, about one half natural size; _b_ longitudinal section through the head.] APPENDIX TO THE ASCOMYCETES: Family 7. =Ascolichenes (Lichen-forming Ascomycetes).= The Lichens were formerly classed among the Thallophyta as a group quite distinct from the Algæ and Fungi. Investigations during the last twenty-five years, however, have conclusively proved that the Lichens are Fungi which reproduce in the same manner as the Ascomycetes, or, more rarely, the Basidiomycetes, and have entered into a peculiar _symbiotic relation with Algæ_, especially the Cyanophyceæ and Protococcoideæ, with which they associate, and without which they would be unable to exist. The Fungus forms the largest portion of the Lichen, enclosing the Alga with which it may be said to be commensal. The Fungus especially produces reproductive bodies and absorbs the inorganic nourishment through the rhizoids, whilst the Alga supplies it with the organic materials. In consequence of this the Lichens, in contradistinction to other Fungi, need light for the development of their nutritive organs, and are therefore, in any case internally, of a more or less greenish colour. The form and condition of the thallus is unusual among the Fungi, and they can grow upon rocks and in other places where no dead organic matter, such as would be required by other Fungi, is obtainable.