86 MYCOLOGY 



the gill surfaces of the Lactarius sp. on which it grows, converting an 

 otherwise grayish-white fruit body into a cinnabar-red one. It is 

 found in the woods about Philadelphia, Pa. The fungi belonging to 

 the family Laboulbeniace^ are included in 28 genera and approxi- 

 mately 152 species, and have been made known largely through the 

 studies of Prof. Roland Thaxter of Harvard University. A few species 

 are found in Europe, in the tropics of Africa, America and Asia, but 

 North America is extraordinarily rich in specific forms. They occur 

 on dipterous, neuropterous and coleopterous insects, especially those 

 which live in damp places or in the water. The corn-smut Ustilago 

 maydis is a parasite confined exclusively to the maize plant, Zea mays, 

 and to the closely related if not identically the same grass the teosinte; 

 EuchlcBna mexicana as pointed out some years ago by the writer^ as 

 proof of the common origin of these two grasses. Wherever maize is 

 cultivated the smut is found associated with it. 



The rusts (Uredine^) are arnong the most specialized of fungi in 

 their parasitic habits, some species being confined to one or two hosts. 

 They ascend with their host plants above the snow line on high moun- 

 tains and toward the poles wherever flowering plants and ferns grow. 

 Whole genera are confined, however, to certain regions. Thus the 

 genus Ravenelia which lives on mimosaceous and caesalpinaceous plants 

 extends north to the 40° north latitude. Many rust fungi are iden- 

 tically the same in North America, north and middle Europe, and of 

 the 500 species known from North America and 400 European rusts 

 approximately 150 species are common to both countries. Only a few 

 Mediterranean species are found in North America, as Uromyces gly- 

 cyrrhizcB and Puccinia Mesneriana. A less number of species are com- 

 mon to North and South America. It is noteworthy that Puccinia 

 malvacearum introduced into Spain from Chile in 1869 has in the forty- 

 six years which have elapsed since its introduction into Europe spread 

 over the world. 



The genus Exohasidium includes 18 species of fungi which cause the 

 formation of fleshy galls chiefly on plants of the family Ericace^. 

 Tabulated the principal species are: 



Exobasidkim laccinii on Vaccinium; Europe, Siberia, America. 

 Exohasidium rhododendri on Rhododendron, Europe, America. 

 1 Harshberger J. W.: Cont. Bot. Lab. Univ. of Pa., 1901: 234. 



