SEPTOBASIDIACEAE 295 



made observations on spore discharge in living material of A. 

 auricula-jiidae and A. mesenterica. . He found that, just as in the 

 Hymenomycetes, a droplet of water is exuded at the base of the 

 spore just before discharge, and that discharge itself is a violent 

 process whereby the spore is thrown through a horizontal dis- 

 tance of 0.4 to 0.5 mm. 



Septobasidiaceae. The Septobasidiaceae includes a number of 

 species possessing transversely septate basidia characteristic of 

 the Auriculariales and having a peculiar biological relationship 

 with scale insects. There are two genera, Uredinella and Septo- 

 basidium. 



Uredinella coccidophaga [Couch (1937)] forms small dark 

 patches on the bark of a number of trees in the southeastern 

 United States. Beneath the stroma of the fundus colony is found 

 a single scale insect (Aspidiotus) the body of which contains 

 fungus haustoria. Over the surface of the mycelium are borne 

 numerous thick-walled hypobasidia, each of which may give rise 

 to a 4-celled epibasidium bearing 4 basidiospores. A second 

 species, U. spimdosa [Couch (1941)], occurring in association 

 with scale insects on Psychotria leaves in Ceylon, has a similar 

 developmental history. 



Couch has studied the cytology of basidial development in 

 Uredinella and refers to the hypobasidium as a teleutospore 

 (tehospore). Thus Uredinella shows a remarkable relationship 

 to the rusts, which is further borne out by the fact that other 

 bodies, superficially resembling the teliospores and formed on 

 the same mycelium, germinate to give rise to elongate, binucleate 

 spores which are perhaps homologous w'lxh rust urediniospores. 

 Couch has suggested that Septobasidium and Uredinella are de- 

 rived from certain of the rusts, such as Goplana. 



The Genus Septobasidium contains approximately 180 species, 

 occurring in large black or brownish patches on the bark of many 

 kinds of living trees in the tropics and subtropics [Couch 

 (1938)]. Whereas Uredinella occurs in association with but a 

 single scale insect, a hundred or more insects may be found 

 within one Septobasidium colony. The insects derive their nour- 

 ishment from the host plant after piercing its bark by means of 

 their sucking mouth parts. The fungus-insect relationship 

 worked out by Couch provides an interesting study in general 

 biological principles. The scale insects become parasitized only 



