PRINCIPAL GROUPS OF PLANTS. 65 



tain localities or at certain periods of the year be the cause of 

 fatal intoxication is answered by Ford in the negative. He states 

 (Science, 30, p. 105, July 23, 1909) that there are no authentic 

 cases of poisoning from the black or brown spored agarics, 

 although old and badly decomposed specimens may cause transient 

 illness. 



Economic Uses of Fungi. A large number of the Fungi, 

 particularly of the Basidiomycetes, are used for food. There 

 are, however, only a few of these which enter the market. These 

 are derived chiefly from Agaricus campestris (Figs. 33 and 34) 

 and Agaricus arvenis, although some other species of Agaricus 

 as well as Morchella esculenta (Fig. 34, 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 Pachytna 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. 29), Poly poms 

 officinalis and other species, and various species of Lycoperdon. 

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

 chirurgonun ) formerly used as a haemostatic, including Lycoper- 

 don Bovista and Polyporus fomentarius. Many of them yield very 

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

 several toxic principles; (2) Lactarius piperatus and others 

 which yield highly poisonous resinous principles. Other uses of 

 Fungi have been mentioned under the several groups. 



USTILAGINE^E 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 the Basidio- 

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

 LTredinese, 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 



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