HYGROCROCIS. 



[ 404 ] 



HYMENOMYCETES. 



Tab. Phyc. pi. 34. fig. 3 ; Rabenhorst, FL 

 Alg. iii. 49. 



HYGROCRO'CIS, Ag. A supposed 

 genus of filamentous Confervas ; apparently- 

 consisting of the flocculent mycelium of 

 Fungi. H. arsenica occurs in solutions of 

 arsenious acid. 



BIBL. Kutzing, Sp. Alg. 148; Raben- 

 horst, FL Alg. ii. 8 (tig.) ; Marchand, Compt. 

 rend. 1878. 



HYME'NIUM. The term applied to 

 the layer of cellular tissue upon which are 

 seated the basidia of the higher FUNGI. 

 The name is also applied to the fructifying 

 stratum in such Ascophorous fungi as Hel- 

 vella, Morchelki, Peziza, &c. 



HYMENO'MONAS, Stein. A genus of 

 Flagellate Infusoria. 



Char. Free, with a crenate, flexible cara- 

 pace j flagella two ; no eye-spot ; lateral 

 yellow-brown pigment bands present. 



H. roseola; length 1-850'': freshwater. 

 (Kent, Inf. 407.) 



HYMENOMYCETES. A tribe of Ba- 

 sidiomycetous Fungi, characterized 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 membra- 

 nous or sometimes gelatinous layer called 

 the hymenium. The fruit, called the re- 

 ceptacle, varies extremely in form. In 

 most of the Tremellini it is an irregular 

 jelly-like or waxy expansion, borne how- 

 ever on a roundish support in Tremella; in 

 the Clavati it forms a club-shaped, mostly 

 branched, fleshy or leathery stalk-like body 

 (called the hymenophore}^ which is clothed 

 at its ends by the sporiferous membrane or 

 hymenium, forming a smooth layer. In 

 the Auriculati and Hydnei the receptacle 

 is either an expanded, 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 Polyporei and Agaricini the receptacle 

 is a discoid (often laminated), bell-shaped 

 or dish-formed, fleshy body, more or less 

 coloured and tuberculated on the upper side, 

 frequently borne on a columnar stalk in- 

 serted on the under side, while the sporife- 

 rous layer, or hymenial structure, presents 

 itself as a conspicuous layer on the under 

 side, consisting of a number of paper-like 

 lamellae, or vertical tubes, prickles, or pits, 

 closely packed, on the lateral surfaces of 

 which are borne the spores; in many 



cases, however, the hymenium is perfectly 

 even in the column. The younger stages 

 of development of some Hymenomycetes 

 do not exhibit all these characters, since 

 the receptacle is at first enclosed in a sac- 

 like body arising from the mycelium, so 

 that the external appearance is similar to 

 that of one of the Gasteromycetes (as in 

 very young mushrooms) ; this sac finally 

 bursts, to allow of the expansion of the 

 receptacle. 



The cellular structure of this family is 

 simple, in spite of the varied outward 

 forms ; the whole mass, from the filamentous 

 mycelium up to the sporiferous membrane 

 or hymenium, is made up of interwoven 

 branched cellular filaments or hyphae, of 

 great tenuity. In the Tremellini these fila- 

 ments are imbedded or dissolved into an 

 amorphous waxy or gelatinous substance ; 

 in other cases they form a dry corky struc- 

 ture ; but the consistence is generally fleshy. 

 In a few cases among the Agaricini and 

 Polyporei, vesicular or elongated branched 

 hyphas of considerable size are met with, 

 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 Polyporei at right 

 angles, requiring a high power for their 

 observation. Four spores are formed on 

 each basidium, from which they fall off 

 when mature. The Agarics exhibit on the 

 hymenium, among the basidia, peculiar pro- 

 jecting vesicles filled with opaque fluid (pol- 

 linaria, Corda ; cystidia, Leveill6 ; utricles, 

 Berkeley), which some have called anthers, 

 but which appear to be paraphyses that 

 is, undeveloped or abortive (bare) basidia. 

 The spores are mostly exceedingly minute, 

 of various forms and colours, and consisting 

 of simple cellules. Tulasne has recently 

 shown that the Tremellini produce sperma- 

 tia, as well as basidiospores j in Tremella, 

 and other genera, they arise from distinct 

 branches of the hymenial filaments ; in 

 Dacrymyces they are produced in germina- 

 tion from some of the detached basidio- 

 spores lying upon the mycelium (see TRE- 

 MELLINI). 



The structure of these Fungi must be 

 investigated in all stages of development, 

 since very great changes of size and 

 form take place at different epochs, simply 



