34 BOTANY AND PHARMACOGNOSY. 



as well as Morchella esculenttt (Fig. 21, illus. 4) furnish excellent 

 products and are cultivated to a limited extent. The " truffles " 

 of the market are tuber-like masses formed under ground, which 

 consist of the ascocarps of certain Tuberaceae, one of the sub- 

 groups of the Ascomycetes, and which are used as a condiment 

 and sometimes roasted like potatoes. Tuckahoe or " Indian 

 bread " is also produced under ground and consists apparently 

 of the fungus Pachyma Cocos and the roots of Liquidambar, the 

 tissues of which have been changed into a compound resembling 

 pectic acid by the fungus. Quite a number of Fungi have been 

 used in medicine, as Claviceps purpurea (Fig. 19), Polyporus 

 officinalis and other species, and various species of Lycoperdon. 

 A number of species are used in making surgeon's agaric (Fungus 

 chirurgorum) formerly used as a hemostatic, including Lycoper- 

 don bovista and Polyporus fomentarius. Many of them yield very 

 toxic principles, as (i) several species of Amanita which contain 

 muscarine or an allied alkaloid; (2) Lactarius piper atus and 

 others which yield highly poisonous resinous principles. Other 

 uses of Fungi have been mentioned under the several groups. 



UsTiLAGiNE^ and Uredine^. — There are two groups of 

 Fungi of considerable economic interest which by some writers 

 are classed by themselves, and by others placed with theBasidio- 

 mycetes. These are the Ustilaginese, or Smut Fungi, and the 

 Uredineae, or Rust Fungi. 



The Smut Fungi are parasitic on higher plants. The myce- 

 lium penetrates the tissues of the host, but does not seem to 

 cause either disease or malformation of the plant. Injury to the 

 host results only after the development of resting spores. The 

 mycelia are hyaline, more or less branched, and finally become 

 septate. They send short branches, called haustoria, into the 

 cells of the host, from which they obtain nourishment. Event- 

 ually the mycelium becomes much branched, compact and more or 

 less gelatinous through a transformation of the hyphal walls, 

 forming gall-like swellings or blisters on the host. Spores are 

 formed within this gelatinous mass at the ends of the branches 

 of the mycelium. At a later stage the smut loses its gelatinous 

 character, the mass breaks up, and the spores are freed and dis- 

 tributed as a dry, dusty powder. The spores (primary conidia) 



