PHLEOGENACEAE 297 



the winter comparatively few of the insects within a colony are 

 parasitized, most of them being entirely free of infection. In the 

 summer, however, as the funfrus forms spores, a majority of the 

 insects become parasitized. Newly born insects are invariably 

 free of infection. 



The advantages of this relationship to the fungus include the 

 food which it obtains from the insect and the spread of the fun- 

 gus through the agency of parasitized insects. The insects also 

 profit from the association, in spite of the fact that some are para- 

 sitized, since the fungus mat offers protection, during reproduc- 

 tion and the rearing of their young, from such natural enemies 

 as birds and parasitic Hymenoptera. Intricate insect houses are 

 formed by some species of Septobasidium. Couch concludes, 

 therefore, that the relationship is one of symbiosis. That the re- 

 lationship is not entirely an obligate one, however, is shown by 

 the fact that the fungus can be grown apart from the insects in 

 pure culture, although under these conditions it will not form 

 spores. 



Some species of Septobasidium have well-developed hypoba- 

 sidia, whereas others lack these structures entirely. The basidium 

 shows considerable variation in structure between species. It 

 may be 1-, 2-, 3-, or 4-celled and may be straight or, as in Helico- 

 basidium, curved. These characteristics, together with specificity 

 of the host, are used in distinguishing the various species of Septo- 

 basidium. 



Phleogenaceae. The Family Phleogenaceae includes a number 

 of auriculariaceous fungi in which the fruiting body consists of a 

 stalk bearing a head. The lower members of the family are gym- 

 nocarpous, but the group culminates in angiocarpous forms. An 

 interesting feature of the family is the fact that sterigmata are not 

 present, the globose basidiospores being formed directly on the 

 basidium. No differentiation of hypobasidium and epibasidium, as 

 occurs in the other families of the Auriculariales, is found in the 

 Phleogenaceae. 



Stilbiim vzilgare was considered to belong among the Fungi Im- 

 perfecti before the study of its development by Juel (1898). Its 

 gymnocarpous fructifications resemble coremia, and the hyphae 

 composing the fruiting body are held together within a gelatinous 

 matrix. The basidia, borne in the bottom of the cup-shaped head, 



