DISCOMYCETES 309 



All the species are minute, rarely exceeding i mm. in 

 length, and the majority are much smaller. Again, all. 

 are external parasites on insects with one exception, which 

 occurs on a member of Arachnida. Beetles are the most 

 favoured hosts, especially aquatic forms or those inhabit- 

 ing damp localities. Some half-dozen species are met 

 with on Dipterous insects, including the common house-fly. 



These parasites, unlike the species of Cordyceps and other 

 fungi parasitic on insects, appear to cause but little incon- 

 venience to the host, and resemble minute, dark-coloured 

 or yellowish bristles projecting from the chitinous integu- 

 ment, singly, in pairs, or densely crowded and forming a 

 furry coating. 



The only known mode of reproduction is of a sexual 

 nature, and has already been described. 



The fundamental structure is simple, consisting in many 

 instances of very few cells differently arranged in different 

 genera; in other genera, however, great diversity, often 

 best expressed by eccentricity, is met with in the arrange- 

 ment of the appendages bearing the male organs. 



The ascospores germinate on the host, becoming attacked 

 by a blackened base which serves as an organ of attach- 

 ment and nutrition. This organ is formed from the lower 

 cell of the two-celled spore. The upper cell of the spore 

 gives origin to the receptacle, which in many simple forms 

 consists of two superposed cells. The upper of these cells 

 gives origin to one or more appendages of very varied form 

 in different genera, and usually bear the antheridia. The 

 female organs are formed from a segment of the lower cell 

 of the receptacle, rarely from the terminal cell. The peri- 

 thecium, as in many other Ascomycetes, originates from a 

 cell of the receptacle situated below the female organ. 



