326 



PART IV.— VEGETABLE TAXONOMY. 



structure of the hymenium, and on the basis of these differences 

 they are classified into the following sub-orders : The Thele- 

 phorece, the Clavariece, the Hydnece, the Polyporece and the Agaric- 

 inece. 



The Thelephorece are, in their structure, the simplest forms of 

 the group. One of the species, Exobasidium Vaccinii, has 

 already been mentioned. In all the hymenium is smooth. They 

 form incrustations, in some species of irregular, in others of 

 regular form, on logs, the bark of trees, etc. 



The Clavariece, or Club-fungi (see Fig. 529), have cylindrical 

 or club-shaped, simple or branching sporocarps, which may, 

 according to the species, be white, grey, brown or yellow in 

 color. The hymenium occupies the smooth exterior surface, 

 and when the spores are ripe, they communicate to it a dusty 

 appearance. 



The Hydnece (see Fig. 530) are distinguished from the rest by 

 the fact that the hymenium consists of prickle-like projections 

 from the surface of the sporocarp. There are many species, 

 some of them having a cap or pileus supported by a central stalk, 

 as in the. common Mushroom; sometimes the stalk is attached 

 laterally, and sometimes there is no stalk. 



The Polyporece are characterized by producing a hymenium 

 which consists of straight tubes arranged compactly side by side. 

 On the inner surface of these tubes the spores are borne. The 

 hymenium covers the under surface. Some of the species pro- 

 duce fructifications of large size. In the genus Polyporus, they 

 mostly form lateral, shelf-like projections which are usually 

 sessile, but sometimes stalked. In the genus Boletus (see Fig. 

 531), there is an expanded cap and a stalk, the latter usually 

 placed centrally. The tough, spongy mycelium of Polyporus 

 formentarius is sometimes used in surgery under the name of 

 Surgeon's Fungus, and, saturated with solution of potassium 

 nitrate and dried, it constitutes what is called German tinder. 

 Polyporus officinalis, a parasite upon the European Larch, has 

 valuable medicinal properties, and Boletus edulis is one among 

 the few of the large genus to which it belongs that is prized for 

 food. 



The Agaricinece produce a sporocarp which is commonly ex- 

 panded and hat-like in form, and in the majority of cases, is 



