DIPLOIDIZATION 281 



mycelium of parasitic species is intercellular, entrance to the host 

 cells being accomplished by haustoria in the rusts. 



Bensaude (1918) pointed out that the mycelium from a single 

 basidiospore may be incapable of giving rise to fructifications, 

 but that two mycelia of opposite potentialities may be adequate. 

 She regarded such species as heterothallic, in contrast to other 

 species in which a single basidiospore is totipotent and which are 

 therefore homothallic. These fundamental differences have been 

 studied and further elaborated by Mounce (1922), Vandendries 

 (1925), Hanna (1925), Newton (1926), Kniep (1928), and 

 others. 



Coprimis lagopits, C. iiarcoticiis, C. iiiveits, and C. stercorarius 

 are among the species found to be homothallic; Armillaria inu- 

 cida, Coprimis fimetar'ms^ certain varieties of C. lagopiis, C. mi- 

 caceiis, Cortichnn poly gomiim, Fomes roseiis, F. sitbroseiis, Len- 

 zites saepiarja, L. trabea, Faneohis campamilatiis^ Schizophyllwn 

 covnmine, and Trametes americaria are heterothallic. 



Mycelia arising from the germination of basidiospores of dif- 

 ferent species differ rather fundamentally. Mycelium from most 

 of the rusts and from Cortic 121771 varians, Colly bia conigena^ and 

 Feniophora sambuci [Kniep (1915, 1917)] consists of uninucleate 

 cells. Mycelium from basidiospores of Feniophora gigantea is 

 also uninucleate, although the basidiospores are themselves bi- 

 nucleate. In this instance one nucleus remains within the spore 

 membrane, and the other migrates into the developing germ tube. 

 The mycelium from basidiospores of Armillaria mucida, Copri- 

 mis fimetariiis, Hypholoma perplexiim, and Fholiota praecox is 

 coenocytic, becoming so by failure of septations to form as the 

 nuclei are undergoing divisions. In Corticiinn bomby cimim (Hy- 

 pochmis terrestris) and in most Gastromycetes the basidiospores 

 are binucleate, and all divisions are conjugate, resulting in di- 

 caryotic mycelium. 



DiPLOiDiZATiON. One peculiarity of the mycelium of the ma- 

 jorits^ of Basidiomycetes is the presence of buckle joints or clamp 

 connections, first noted by Hoffman in 1856 and called "Schnal- 

 lenzellen."- Accord has not been reached on their function and 

 significance. Usually they occur in connection with dicaryotic 

 mycelium only. They are always present at all septa in Daedalea 

 imicolor, Fistiilina hepatica, Lejizites abietimis, and Meniliiis 

 lacrymans and occur at only occasional septa in Coniophora cere- 



