132 FIRST GROUP. THALLOPHYTES. 



club-shaped form and become sporiferous basidia ; each basidium produces two or 

 more, usually four, sometimes eight spores simultaneously ; for this purpose it sends 

 out short slender branches which at first look like papillae, the sterigmafa, and these 

 swell at their free extremity into a round or ellipsoidal shape; the swollen part 

 becomes invested with a firmer cell-wall, and is now a spore on a slender pedicel, and 

 ultimately drops off. 



The basidia are produced simultaneously in great numbers, and are usually 

 crowded together and parallel to one another ; in this way hymenia are formed, which 

 in the Hymenomycetes have sterile filaments (paraphyses) between the basidia, like 

 those of the Discomycetes. The Basidiomycetes are divided into gymnocarpous and 

 angiocarpous forms, according as the hymenia cover free outer surfaces of the fructi- 

 fication, or line cavities in its inner tissue or are otherwise disposed inside it. 



Most Basidiomycetes live on humus or soils containing humus, or their mycelia 

 are developed in old wood or in the bark of the stout stems of living trees ; small 

 forms make use of fallen leaves, rotting branches, and similar matter as a substratum. 

 A few only are true parasites on living plants. 



The following account will serve to draw attention to some of the most dissimilar and 

 morphologically most important fructifications. 



1. Exobasidium Vaccinii 1 shows the simplest mode of fructification. The 

 mycelium is parasitic in the leaves and stems of Vaccinium uilis idaea, and forms a 

 hymenium of closely-packed four-spored basidia directly on the surface of the organs 

 which it has attacked. 



2. The TREMELIiINE AE growing on dead wood or on old stems of living trees 

 form fructifications of gelatinous consistence and often indefinite form, appearing 

 usually as thick wavy coatings. Slender hyphae spread through the jelly and form 

 hymenia on its surface. The mode of forming the spores is more complicated than in 

 other Basidiomycetes 2 . 



3. Among the HYMETSTOMYCETES 3 those which form a cap (pileus), the Cap- 

 fungi, are the best known and the most common. The structure which is usually 

 called the Fungus or mushroom is the gonidiophore, and springs from a mycelium 

 which vegetates in the ground or on wood or some other substance. The pileus is 

 usually but not always stalked. The hymenial layer is on projecting portions of the 

 substance of the pileus on its under surface, and these projections are of various form ; 

 in the genus Agaricus they are numerous vertical gills (lamellae) running in a radial 

 direction from the stalk (stipe} to the margin of the pileus ; in Cyclomyces similar lamellae 

 form concentric circles ; in Polyporus and Daedalea they are connected together 

 so as to form a network ; in Boletus they form closely-packed vertical tubes, which in 

 Fistulina are isolated ; in Hydnum the under side of the pileus is beset with soft 

 dependent spikes, like icicles, which carry the hymenium on their surface. In many 

 cases the fructification is naked, in others a veil which is subsequently torn away 

 stretches across the under side of the pileus (cortina, velum partiale), or pileus and 

 stipe are enveloped in a similar wrapper (vo/va, velum universale), or lastly in some 

 species, as Amanita, both membranes are present. These veil-formations are connected 

 with the entire growth of the fructification ; the species with a naked pileus are by their 

 nature gymnocarpous, the veiled species afiford a transition to the angiocarpous 



1 Woronin, in Ber. d. naturf. Ges. zu Freiburg i. Br., Bd. IV. 1867. 



2 Tulasne, in Ann. d. sc. nat. 3" ser. T. XIX, and 5" ser. T. XV. Brefeld, he. at. III. Heft. 



3 [De Bary, Vergl. Morph. u. Biol. d. Pilze, 1884, p. 366 (literature).] 



