410 GEOGRAPHICAL DISTRIBUTION OF FUNGI 



Another feature reeardins the distribution of Basidiomvcetes 

 that has impressed every mycologist who has intensively collected 

 in a given area for a period of years is that certain species found 

 one season mav be entirely absent in succeeding years. 



The extensive studies of Overholts (1939) led him to conclude 

 that of the 227 species of North American pileate Polyporaceae 

 at least 43% occur in the Eastern Hemisphere. Of the more com- 

 mon genera, he found that 54 0/ of Fomes and of Trametes species, 

 50% of Daedalea and of Lenzites species, and 44% of Polyporus 

 species are common to North America and the Old World. Cer- 

 tain of them, such as Polyporus conchifer and P. texam/s, are 

 limited in range to that of their hosts, Uhmis americana and 

 Prosopis jttliflora, respectively. Fomes applanatus is a cosmopoli- 

 tan species. Polyporus abietinus can utilize all species of conifers; 

 P. versicolor, P. pargamemis, and Lenzites bctid'nw, many kinds of 

 hardwoods; and all are widely distributed. Fomes pint and Poly- 

 poms schweinitzii, both capable of causing heart rots of conifers, 

 are widely present throughout the United States and Canada. 



The Gastromycetes are widely dispersed, with little evidence 

 of being affected by latitude. An exception is the Phallales, which 

 are mostly tropical, whereas the Lycoperdales are temperate. 



DISTRIBUTION OF DEUTEROMYCETES 



The imperfect fungi of most economic importance are either 

 seed-borne or soil-borne or else are dispersed with nursery stock. 



Distribution of seed-borne species. Many pathogenic im- 

 perfect fungi, particularly those of cultivated plants, have been 

 demonstrated to be seed-borne [Orton (1931)]. This fact ac- 

 counts for the wide distribution and establishment of such fungi 

 as Ascochyta pisi, leaf and pod blight of pea; Cercospora beticola, 

 leaf spot of beet; Cercospora daizu, frog-eye leaf spot of soybean; 

 Collet otrichum gossypii, cotton anthracnose; C. lagenarium, water- 

 melon anthracnose; C. I'mdemuthiamivi, bean anthracnose; Clado- 

 sporinm fulvum, leaf mold of tomato; Diplodia zeae, ear rot of 

 corn; Kabatiella caidivora, anthracnose of clover; Helvnntho- 

 sporhim graminenm, barley stripe; Phoma I'm gam, cabbage black- 

 leg; Polyspora Urn, flax-stem break; Septoria apii, celery blight; 

 Septoria ly coper sic'i, leaf spot of tomato. Presumably each of 

 these fungi occurs wherever its hosts are cultivated, and com- 



