Fig. 3.—a. Sterile cells. b. Basidia. c. Cystidium. From Gomphidius (de Seynes).
The cystidia are usually larger than the basidia, varying in size and form in different species. They present the appearance of large sterile cells, attenuated upwards, sometimes into a slender neck. Corda was of opinion that these were male organs, and gave them the name of pollinaires. Hoffmann has also described[F] both these organs under the names of pollinaria and spermatia, but does not appear to recognize in them the sexual elements which those names would indicate; whilst de Seynes suggests that the cystidia are only organs returned to vegetative functions by a sort of hypertrophy of the basidia.[G] This view seems to be supported by the fact that, in the section Pluteus and some others, the cystidia are surmounted by short horns resembling sterigmata. Hoffmann has also indicated[H] the passage of cystidia into basidia. The evidence seems to be in favour of regarding the cystidia as barren conditions of basidia. There are to be found upon the hymenium of Agarics a third kind of elongated cells, called by Corda[I] basilary cells, and by Hoffmann “sterile cells,” which are either equal in size or smaller than the basidia, with which also their structure agrees, excepting in the development of spicules. These are the “proper cells of the hymenium” of Léveillé, and are simply the terminal cells of the gill structure—cells which, under vigorous conditions, might be developed into basidia, but which are commonly arrested in their development. As suggested by de Seynes, the hymenium seems to be reduced to great simplicity, “one sole and self-same organ is the basis of it; according as it experiences an arrest of development, as it grows and fructifies, or as it becomes hypertrophied, it gives us a paraphyse, a basidium, or a cystidium—in other terms, atrophied basidium, normal basidium and hypertrophied basidium; these are the three elements which form the hymenium.”[J]
The only reproductive organs hitherto demonstrated in Agarics are the spores, or, as sometimes called, from their method of production, basidiospores.[K] These are at first colourless, but afterwards acquire the colour peculiar to the species. In size and form they are, within certain limits, exceedingly variable, although form and size are tolerably constant in the same species. At first all are globose; as they mature, the majority are ovoid or elliptic; some are fusiform, with regularly attenuated extremities. In Hygrophorus they are rather irregular, reniform, or compressed in the middle. Sometimes the external surface is rough with more or less projecting warts. Some mycologists are of opinion that the covering of the spore is double, consisting of an exospore and an endospore, the latter being very fine and delicate. In other orders the double coating of the spore has been demonstrated. When the spore is coloured, the external membrane alone appears to possess colour, the endospore being constantly hyaline. It may be added here, that in this order the spore is simple and unicellular. In Lactarius and Russula the trama, or inner substance, is vesicular. True latex vessels occur occasionally in Agaricus, though not filled with milk as in Lactarius.
Fig. 4.—Polyporus giganteus (reduced).
Polyporei.—In this order the gill plates are replaced by tubes or pores, the interior of which is lined by the hymenium; indications of this structure having already been exhibited in some of the lower Agaricini. In many cases the stem is suppressed. The substance is fleshy in Boletus, but in Polyporus the greater number of species are leathery or corky, and more persistent. The basidia, spicules, and quaternate spores agree with those of Agaricini.[L] In fact there are no features of importance which relate to the hymenium in any order of Hymenomycetes (the Tremellini excepted) differing from the same organ in Agaricini, unless it be the absence of cystidia.
Fig. 5.—Hydnum repandum.
Hydnei.—Instead of pores, in this order the hymenium is spread over the surface of spines, prickles, or warts.[M]