DISTRIBUTION OF BASIDIOMYCETES 405 



Also, Ophionectria cylindrothecia is abundant on sterns of pal- 

 metto palm in Bermuda [Seaver (1942)] and has been found on 

 cornstalks in Ohio. 



Many fungi are limited to particular substrata, but the under- 

 lying reasons for this limitation are unknown. None of the spe- 

 cies of Melanconis, Pseudovalsa, Prosthecium, and Titania occurs 

 on coniferous wood [Wehmeyer (1941)], whereas each species 

 of Keithia is limited to a certain conifer. Keithia tetraspora occurs 

 on Juniperus communis, K. jnniperi on Jwiiperus virginiana, K. 

 tsugae on Tsuga canadensis, K. thujina on Tlnija occidentalism and 

 K. chaviaecyparissi on Chamaecyparis thyoides. 



Until more is known about the reasons for differences between 

 host species and varieties in susceptibility to a given fungus and 

 about the influence of environment on the aggressiveness or viru- 

 lence of pathogenic fungi, no one can prophesy the probable out- 

 come of their introduction into new areas. Lophoderminm 

 pinastri, for instance, has long been known in Europe as a serious 

 menace in pine-seedling nurseries, but, although this fungus is 

 not uncommon in the United States, it is as yet nowhere a major 

 problem. 



DISTRIBUTION OF BASIDIOMYCETES 



Obligate parasitism, as correlated with host range, is a primary 

 factor in accounting for the distribution of the smuts and rusts. 

 This is not so, however, among Hymenomycetes and Gastro- 

 mycetes generally, even among those that are not saprophytic. 



Distribution of smuts. The monograph by Clinton (1906) 

 contains 206 species of smuts, of which 114 are strictly North 

 American. Several of the smuts, including Ustilago zeae on maize 

 and the stinking smuts of wheat, Tilletia foetans and T. tritici 

 [Holton and Heald (1941)], are now and have been for a con- 

 siderable period essentially coextensive in range with that of their 

 host. Certain others are less widely dispersed. These include 

 Tilletia horrida on rice, which is endemic in China and is known 

 also from Indo-China, Burma, the Philippine Islands, and adjacent 

 tropical and subtropical areas. It was first introduced during the 

 late 1890's into South Carolina with seed rice sent from China 

 [Anderson (1899)]. Subsequently it has spread to Louisiana and 

 Arkansas. Another smut, alien to the United States, is Urocystis 

 tritici, causing flag smut of wheat. In all likelihood this smut is 



