412 GEOGRAPHICAL DISTRIBUTION OF FUNGI 



the Texas root-rot fungus. The appropriateness of its specific 

 name is indicated by the fact that it is known to attack more than 

 1 700 species of flowering plants, more than does any other known 

 pathogen. An appreciation of the destructiveness of P. omni- 

 vorum can be gained from the fact that a complete bibliography 

 of it would include about 300 titles, and annual losses which it 

 occasions are estimated to approximate one hundred million 

 dollars. 



Its range extends throughout the greater part of Texas and con- 

 tiguous parts of Arkansas, Oklahoma, New Mexico, and .Mexico. 

 It also occupies areas in Arizona, California, Nevada, and Utah. 

 Its existence outside this range has been noted in the Dominican 

 Republic, Hawaii, and (doubtfully) Russia. 



Active dissemination is accomplished largely bv growth of the 

 fungus through the soil, where it may hibernate by means of 

 sclerotia. 



Various species of Fusarium that live saprophytically in the soil 

 for long periods and cause wilt diseases when the appropriate 

 crop is'planted on such a soil are also included in this group. 

 Among them are Fusarium vasinfectum on cotton, F. cubense on 

 banana, F. oxysporum on potato, F. lycopersici on tomato, F. 

 niveum on watermelon, and F. lini on flax. All are widely dis- 

 persed in any region where these crops are grown. 



IMPLICATIONS 



It is quite apparent that no comprehensive information regard- 

 ing fungus floras throughout the world is available at this time. 

 Many additional monographic studies of fungal groups must first 

 be made, and also many more lists of the type of the Host Index 

 of the Fungiof North America [Seymour ( 1929)], The Fungi of 

 Manitoba [Bisbv, Buller, and Dearness (1929)], The Fungi of 

 India [Butler and Bisby (1931)], and British Stem and Leaf Fungi 

 [Grove (1935, 1937)] must be prepared. Seymour's book in- 

 cludes about half of all the known species of fungi, and about 

 60 c of the Canadian species listed by Bisby et al. (1929) are also 

 known to occur in Europe. 



Students of the geographic distribution of fungi seem agreed 

 that climate has a controlling effect [Bisby ( 1943) ], Diehl (1937), 

 Lind (1934). Diehl (1937) concluded that the life zones of 



