The four remaining orders, though large, can be easily characterized. In _Tuberacei_, all the species are subterranean, and the hymenium is mostly sinuated. In _Elvellacei_, the substance is more or less fleshy, and the hymenium is exposed. In _Phacidiacei_, the substance is hard or leathery, and the hymenium is soon exposed. And in _Sphæriacei_, although the substance is variable, the hymenium is never exposed, being enclosed in perithecia with a distinct opening at the apex, through which the mature spores escape. Each of these four orders must be examined more in detail. The _Tuberacei_, or subterranean _Ascomycetes_, are analogous to the _Hypogæi_ of the _Gasteromycetes_. The truffle is a familiar and highly prized example. There is a kind of outer peridium, and the interior consists of a fleshy hymenium, more or less convoluted, sometimes sinuous and confluent, so as to leave only minute elongated and irregular cavities, and sometimes none at all, the two opposing faces of the hymenium meeting and coalescing.[S] Certain privileged cells of the hymenium swell, and ultimately become asci, enclosing a definite number of sporidia. The sporidia in many cases are large, reticulated, echinulate or verrucose, and mostly somewhat globose. In the genus _Elaphomyces_, the asci are more than commonly diffluent. The _Elvellacei_ are fleshy in substance, or somewhat waxy, sometimes tremelloid. There is no peridium, but the hymenium is always exposed. There is a great variety of forms, some being pileate, and others cup-shaped, as there is also a great variation in size, from the minute _Peziza_, small as a grain of sand, to the large _Helvella gigas_, which equals in dimensions the head of a child. In the pileate forms, the stroma is fleshy and highly developed; in the cup-shaped, it is reduced to the external cells of the cup which enclose the hymenium. The hymenium itself consists of elongated fertile cells, or asci, mixed with linear thread-like barren cells, called paraphyses, which are regarded by some authors as barren asci. These are placed side by side in juxtaposition with the apex outwards. Each ascus contains a definite number of sporidia, which are sometimes coloured. When mature, the asci explode above, and the sporidia may be seen escaping like a miniature cloud of smoke in the light of the mid-day sun. The disc or surface of the hymenium is often brightly coloured in the genus _Peziza_; tints of orange, red, and brown having the predominance.