102 EFFECTS OF TEMPERATURE ON FUNGI 



may completely invade the wood to the exclusion of all other 

 Thelephoraceae and Polvporaceae. Conceivably the temperature 

 differential may be an important factor when two or more species 

 are competing for occupancy of a given piece of wood, but it may 

 not necessarily constitute the controlling factor. 



Another inference from the data of Cartwright and Findlay 

 (1934) involves temperature as an ecological factor affecting the 

 geographical distribution of fungi. It is well known that certain 

 species, just as is true also of seed plants, are quite sharply re- 

 stricted in their natural habitat to Arctic regions, to temperate 

 regions, or to the tropics. In pathogens this distribution might be 

 anticipated to be coextensive with that of the suscepts and there- 

 fore not necessarily governed primarily by temperature. In sapro- 

 phytic species, temperature might not be expected to be as potent 

 a factor as the kind of substrate, and saprophytes might be antici- 

 pated to be cosmopolitan in distribution. Nevertheless, many 

 saprophytes are restricted in distribution, but evidence indicates 

 that with them temperature is a major factor. This conclusion 

 finds support in Weimer and Harter's (1923) studies on the tem- 

 perature relations among species of Rhizopus. They found that 

 R. chinensis is distinctly more tolerant of high temperature than 

 any of the other ten species tested. 



Humphrey and Siggers (1933) made an extensive study of tem- 

 peratures favorable to the growth of wood-rotting fungi in cul- 

 ture, and on this basis were able to arrange them into three groups: 

 (1) a low-temperature group (20° to 24° C), (2) an intermediate- 

 temperature group (24° to 32° C), and (3) a high-temperature 

 group (above 32° C). 



In the first group are included Coniophora cerebella, Stereum 

 gausapatuni, Merulius lacrymans, Phlebia merismoides, Folypoms 

 abietiiuts, P. schnveinitzii, Tomes amiosus, F. officinalis, F. mgroli- 

 neatns, Trametes pini, and Colly bia velutipes. In the second group 

 Humphrey and Siggers placed Merulius sihestris, At. tremellosus, 

 Corticium chrysocreas, C. effuscatum, Peniophora gigantea, 

 Stereiim jrustulosum, S. fasciatum, S. rameale, Porta incrassata, P. 

 subacida, P. xantha, Polyporus radiatus, P. robinophilus, P. sinuo- 

 sus y P. sulphireus, P. versicolor, Daedalea ambigua, D. quercina, 

 D. unicolor, Trametes serialis, Tomes everhartii, F. igniarius, F. 

 marmoratus, F . pijiicola, F. rimosus, F. subroseus, Ganoderma 

 applanatum, Lenzites berkeleyi, Irpex mollis, Hydnum ochracewn, 



