first under the form of a small rounded globule, and almost entirely cellular. This small globule, the commencement of the receptacle, is not long in increasing, preserving its rounded form up to the development of the asci. At this period, under the influence of the rapid growth of these organs, it soon produces at its summit a fissure of the external membrane, which becomes a more marked depression in the marginate species. The receptacle thus formed increases rapidly, becomes plane, more convex, or more or less undulated at the margin, if at all of large size. Fixed to the place where it is generated by some more or less abundant mycelioid filaments, the receptacle becomes somewhat cup-shaped and either stipitate or sessile, composed of the receptacle proper and the hymenium.

The receptacle proper comprehends the subhymenial tissue, the parenchyma, and the external membrane. The subhymenial

FIG. 33.-Section of cup of Ascobolus. a. External cells. b. Secondary layer. c. Subhymenial tissue (Janczenski).

tissue is composed of small compact cells, forming generally a more coloured and dense stratum, the superior cells of which give rise to the asci and paraphyses. The parenchyma is seated beneath this, and is generally of interlaced filaments, of a looser consistency than the preceding, united by intermediate cellules. The external membrane, which envelopes the parenchyma, and limits the hymenium, differs from the preceding by the cells often being polyhedric, sometimes transverse, and united together, and sometimes separable. Externally it is sometimes smooth, and sometimes granular or hairy.

The hymenium is, however, the most important part, consisting of (1) the paraphyses, (2) the asci, and sometimes (3) an investing mucilage. The asci are always present, the paraphyses are sometimes rare, and the mucilage in many cases seems to be entirely wanting.

The paraphyses, which are formed at the first commencement of the receptacle, are at first very short, but soon elongate, and become wholly developed before the appearance of the asci. They are linear, sometimes branched and sometimes simple, often more or less thickened at their tips; almost always they contain within them some oleaginous granules, either coloured or colourless. Their special function seems still somewhat obscure, and Boudier suggests that they may be excitatory organs for the dehiscence of the asci. However this may be, some mycologists are of opinion that, at least in some of the Ascomycetes, the paraphyses are abortive asci, or, at any rate, that abortive asci mixed with the paraphyses cannot be distinguished from them.

The mucilage forms itself almost at the same time as the paraphyses, and previous to the formation of the asci. This substance appears as a colourless or yellowish mucilage, which envelopes the paraphyses and asci, and so covers the hymenium with a shining coat.

The asci appear first at the base of the paraphyses, under the form of oblong cells, filled with colourless protoplasm. By rapid growth, they soon attain a considerable size and fulness, the protoplasm being gradually absorbed by the sporidia, the first indication of which is always the central nucleus. The mucilage also partly disappears, and the asci, attaining their maturity, become quite distinct, each enclosing its sporidia. But before they take their complete growth they detach themselves from the subhymenial tissue, and being attenuated towards their base, are forced upwards by pressure of the younger asci, to, and in some instances beyond, the upper surface of the disc. This phenomenon commences during the night, and continues during the night and all the morning. It attains its height at mid-day, and it is then that the slightest breath of air, the slightest

movement, suffices to cause dehiscence, which is generally followed by a scarcely perceptible contractile motion of the receptacle.

There is manifestly a succession in formation and maturity of the asci in a receptacle. In the true Ascobolei, in which the sporidia are coloured, this may be more dis

tinctly seen. At first some thin projecting points appear upon the disc, the next day they are more numerous, and become more and more so on following days, so as to render the disc almost covered with raised black or crystalline points;* these afterwards diminish day by day, until they ultimately cease. The asci, after separation from the subhymenial tissue, continue to lengthen, or it may be that their elasticity permits of extension during expulsion. Boudier considers that an amount of elasticity is certain, because he has seen an ascus arrive at maturity, eject its spores, and then make a sharp and considerable movement of retraction, then the ascus returned again immediately towards its previous limits, always with a reduction in the number of its contained sporidia.

The dehiscence of the asci takes place in the Ascobolei, in some species of Peziza, Morchella, Helvella, and Verpa, by means of ar apical operculum, and in other Peziza, Helotium, Geoglossum, Leotia, Mitrula, &c., by a fissure of the ascus. This operculum may be the more readily seen when the ascus is coloured by a drop of tincture of iodine.

and paraphyses of Asco

FIG. 34.-Asci, sporidia, bolus (Boudier).

The sporidia are usually four or eight, or some multiple of that number, in each ascus, rarely four, most commonly eight. At a fixed time the protoplasm, which at first filled the asci, disOnly in some of the Discomycetes are the asci exserted.

*

appears or is absorbed in a mucilaginous matter, which occupies its place, in the midst of which is a small nucleus, which is the rudiment of the first spore; other spores are formed consecutively, and then the substance separates into as many sections as there are sporidia. From this period each sporidium seems to have a separate existence. All have a nucleus, which is scarcely visible, often slightly granular, but which is quite distinct from the oleaginous sporidioles so frequent amongst the Discomycetes, and which are sometimes called by the same name. The sporidia are at first a little smaller than when mature, and are surrounded by mucilage. After this period the sporidia lose their nebulous granulations, whilst still preserving their nucleus; their outlines are distinct, and, amongst the true Ascobolei, commence acquiring a rosy colour, the first intimation of maturity. This colour manifests itself rapidly, accumulating exclusively upon the epispore, which becomes of a deep rose, then violet, and finally violet blue, so deep as sometimes to appear quite black. There are some modifications in this coloration, since, in some species, it passes from a vinous red to grey, then to black, or from rose-violet to brown.

The epispore acquires a waxy consistence by this pigmentation, so that it may be detached in granules. It is to this particular consistency of the epispore that the cracks so frequent in the coloured sporidia of Ascobolus are due, through contraction of the epispore. As they approach maturity, the sporidia accumulate towards the apex of the asci, and finally escape in the manner already indicated.

In all essential particulars there is a great similarity in the structure of the other Discomycetes, especially in their reproductive system. In most of them coloured sporidia are rare. In some the receptacle is pileate, clavate, or inflated, whilst in Stictis it is very much reduced, and in the lowest form of all, Ascomyces, it is entirely absent. In the Phacidiacei, the structure is very similar to that of the Elvellacei, whilst the Hysteriacei, with greater affinities with the latter, still tend towards the Pyrenomycetes by the more horny nature of the receptacle, and the greater tendency of the hymenium to remain closed, at

least when dry. In some species of Hysterium, the sporidia are remarkably fine. M. Duby* has subjected this group to ex

amination, and M. Tulasne partly so.†

SPHERIACEI. In this group there is considerable variation, within certain limits. It contains an immense number of species, and these are daily being augmented. The general feature in all is the presence of a perithecium, which contains and encloses the hymenium, and at length opening by a pore or ostiolum at the apex. In some the perithecia are simple, in others compound; in some immersed in a stroma, in others free; in some fleshy or waxy, in others carbonaceous, and in others membranaceous. But in all there is this important difference from the Ascomycetes we have already had under consideration, that the hymenium is never exposed. The perithecium consists usually of an external layer of cellular structure, which is either smooth or hairy, usually blackish, and an internal stratum of less compact cells, which give rise to the hymenium.

FIG. 35.-Perithecium of Sphæria and Section.

As in the Discomycetes, the hymenium consists of asci, paraphyses, and mucilage, but the whole forms a less compact and more gelatinous mass within the perithecium. The formation and growth of the asci and sporidia differ little from what we have described, and when mature the asci dehisce, and the sporidia alone are ejected from the ostiolum. We are not aware that operculate asci have yet been detected. It has been shown in some instances, and suspected in others, that certain moulds, formerly classed with Mucedines and Dematiei, especially in the genus Helminthosporium, bear the conidia of species of Sphæria, so that this may be regarded as one form of fruit.

Perithecia, very similar externally to those of Sphæria, but containing spores borne on slender pedicels and not enclosed in asci, have had their relations to certain species of Sphæria indi*Duby, "Mémoire sur la Tribu des Hysterinées," 1861. Tulasne,"Select a Fungorum Carpologia," vol. iii.