HYMENODECTON. 



[ 333 ] 



HYMENOMYCETES. 



layer of cellular tissue upon which are seated 

 the busidia of the higher Fungi. 



HYMENODECTON, Leightou. — A 

 genus of Graphideae (Gymnocarpous Li- 

 chens), separated from Opegrapha. H. (Op.) 

 dendritic a and its varieties occur on the 

 bark of beech trees. 



BiBL. Leighton, Ann. Nat. Hist. 2nd ser. 

 xiii. p. 387; Eng. Bot. pi. 1756. 



HYMENOMYCETES. — The highest 

 order of Fungi, characterized scientifically 

 by the peculiar mode of arrangement of the 

 spores, which are borne in groups of four on 

 the exposed surface of a more or less mem- 

 branous or sometimes gelatinous layer called 

 the hymenium. The fruit, called the sporan- 

 gium, varies extremel}^ in form. In most of 

 the Tremellini it is an irregular jelly-like or 

 waxy expansion, borne, however, on a round- 

 ish support in Tremella ; in the Clavati it 

 forms a club-shaped, mostly branched, fleshy 

 or leathery stalk-like body (called the hyme- 

 nophore), which is clothed at its ends by the 

 sporiferous-membrane or hymenium, forming 

 a smooth layer. In the Auriculati and 

 Ilydnei the sporangium is either an ex- 

 panded irregular crust-like, membranous or 

 leathery mass, or has the form of a club, a 

 funnel, or of a hat or cap, the sporiferous 

 membrane clothing either the upper or under 

 surface as a warty, spiny or comb-like stratum. 

 In Polypori and Agarici the sporangium 

 is a discoid (often laminated), bell-shaped, 

 or dish-formed, fleshy body, more or less 

 coloured and tuberculated on the upper side, 

 mostly borne on a columnar stalk inserted 

 on the under side, w hile the sporiferous layer, 

 or hymenial structure, presents itself as a 

 conspicuous layer on the under side, con- 

 sisting of a number of paper -like lamellae, or 

 vertical tubes or pits, closely packed, on the 

 lateral siu'faces of which are borne the spores. 

 The younger stages of development of most 

 Hymenomycetes do not exhibit all these 

 characters, since the sporange is at first en- 

 closed in a sac-like body arising from the 

 m} celium, so that the external appearance is 

 similar to that of one of the Gymnoraycetes 

 (as in very young mushrooms) ; this sac 

 finally bursts, to allow of the expansion of 

 the sporangium. 



The cellular structure of this family is 

 simple, in spite of the varied outward forms ; 

 the whole mass, from the filamentous myce- 

 lium up to the sporiferous membrane or hy- 

 menium, is made up of interwoven branched 

 cellular filaments, of great tenuity. In the 

 TremelHni these filaments are imbedded or 



dissolved into an amorphous waxy or gela- 

 tinous substance ; in other cases they form 

 a dry, corky structure, but the consistence is 

 generally fleshy. In a few cases among the 

 Agarici and Polypori, vesicular or elongated 

 branched cells are met with, of considerable 

 size, containing a milky juice (in the gills 

 of Ag.deliciosus, &c.). The spores are short 

 terminal branches of roundish or elongated 

 cells, called basidia, clothing the free surface 

 of the hymenial structure (see Basidio- 

 SPOREs). They may be seen in thin cross 

 sections cutting the laminae of the Agarics 

 or the tubes of the Polypori at right angles, 

 requiring a high power for their observation. 

 Four spores are formed on each basidium, 

 from which they fall ofi' when mature. The 

 Agarics exhibit on the hymenium, among 

 the basidia, peculiar projecting vesicles filled 

 with opake ^uid {pollinaria, Corda; cystidia, 

 Leveille; utricles, Berkeley), which some 

 have called anthers, but which appear to be 

 paraphyses, that is, undeveloped or abortive 

 (bare) basidia. The spores are mostly ex- 

 ceedingly minute, of various forms and co- 

 lours, and consisting of simple cellules. 

 Tulasne has recently shown that the Tre- 

 mellini produce spermatia as well as basidio- 

 spores ; in Tremella, and other genera, they 

 arise from distinct branches of the hymenial 

 filaments ; in Dacrymyces they are produced 

 in germination from some of the detached 

 basidiospores lying upon the mycelium (see 

 Tremellini). 



The structure of these Fungi must be in- 

 vestigated in all stages of development, since 

 very great changes of size and form take 

 place at diff'erent epochs, simply from expan- 

 sion or solution of the cellular textures. 



Synopsis of the Tribes. 



1. Agaricini. Sporange like a round or 

 flat cap, borne on a stalk. Hymenium form- 

 ing vertical plates or folds on the under 

 surface. 



2. Polyporei. Sporange like a round 

 or flat cap, disk, cup, or funnel, sometimes 

 stalked, with a porous (formed of tubes) or 

 reticulated hymenium on the under side. 



3. Hydnei. Sporange like a round or 

 flat cap, cup, or funnel, sometimes stalked, 

 with the hymenium on the under side exhi- 

 biting awl-shaped processes or tubercles. 



4. AuRTCULARiNi. Sporaugc tubular, 

 cup- or funnel-shaped, with the smooth or 

 papillose hymenium on the under surface. 



5. Clavati. Sporanges club-shaped, 

 simple or branched like a shrub, with the 



