LABOULBENIALES 2S3 



Laboulbeniales 



The Laboulbeniales comprise a group of peculiar pyrenomyce- 

 tous fungi that are obligate parasites of insects. Knowledge of 

 the group, in which some 50 genera and 1250 species are known 

 at present, is almost entirely the result of the researches of Thax- 

 ter (1895, 1908, 1924, 1926, 1931). Although most members of 

 the order are parasitic upon Coleoptera, a few are to be found 

 upon Hymenoptera, Diptera, and other groups of insects. 



The Laboulbeniales are characteristically ectoparasites upon 

 the chitinous exoskeleton or integument of their hosts. The 

 various species of fungi are limited not only to definite host 

 genera and species, but also in a few instances to a definite and 

 restricted area upon its host; for example, some species occurring 

 upon the right wing cover of a beetle are not to be found in a 

 corresponding position upon the left elytron. The plant body 

 is attached to the chitinous integument by means of a "foot," 

 which in the vast majority of species does not penetrate within 

 the body cavity of the insect. Hence, unlike most other ento- 

 mogenous fungi, the Laboulbeniales are not fatal to their hosts, 

 which suffer little injury from infection. The role of the foot 

 in the nutrition of the fungus is a question much in dispute. 



The plant body consists essentially of a row of cells, arising 

 from the foot, bearing a female reproductive branch and giving 

 rise laterally to filamentous appendages on which are borne the 

 antheridia. 



Reproduction. Sterile appendages similar to those bearing an- 

 theridia may occur throughout the order. It is upon the basis 

 of the antheridia that the Laboulbeniales have been classified. 

 Uninucleate spermatia are produced throughout the order. In 

 the primitive Family Ceratomycetaceae the spermatia are borne 

 exogenously on the antheridial branches. In the Laboulbeniaceae 

 the spermatia are formed endogenously within flask-shaped an- 

 theridia. In the Peyritschiellaceae the antheridia are compound, 

 and the endogenous spermatia are discharged into a common 

 cavity. 



The female reproductive branch, or archicarp, consists of a 

 trichogyne, trichophore cell, and carpogenic cell. The carpo- 

 genic cell produces from 1 to 32 ascogenous cells; ascogenous 



