236 THE ASCOMYCETES 



Laboulbeniales as reduced and specialized forms, differing rather 

 widely from other Ascomycetes. 



LITERATURE CITED 



Faull, J. H., "The cytology of the Laboulbeniales," Aim. Botany, 25: 649- 



654, 1911. 

 "The cytology of Laboitlbenia cbaetopbora and L. Gyrmidanmi,^'' Ann. 



Botany, 26:125-155, 1912. 

 Thaxter, R., "Contribution to\vard a monograph of the Laboulbeniaceae," 



Part 1, Mem. Am. Acad. Arts Sci., 12^95-^29, 1895; Part 2, i5;219- 



469, 1908; Part 3, i-/; 309-426, 1924; Part 4, 2 T; 427-580, 1926; Part 5, 



16: 1-435, 1931. 



Heijjisphaeriales 



The Hemisphaeriales comprise an artificial assemblage of five 

 families which resemble both Pyrenomycetes and Phacidiales 

 and are therefore regarded as intermediate between the pyreno- 

 mycetous and discomycetous fungi. Their fructifications are 

 shield-shaped, lack ostiola, and hence rupture irregularly, and 

 their supporting hyphae are for the most part radiately arranged. 

 Certain mycologists have res^arded such fructifications as the 

 lower half of inverted perithecia, the morphologic base being 

 attached to the hyphae above and the upper part having atro- 

 phied in response to protection afforded by attachment to the 

 host tissues. To such structures, the name thyriothecia has 

 been applied. 



The Hemisphaeriales generally are parasitic on leaves of plants. 

 The larger number are tropical, but collectors familiar with the 

 order are finding them not uncommon in the Temperate zones. 

 Relatively few are known to possess conidial stages. In their 

 monographic treatment Theissen and Sydow (1917) recognize 

 over 300 species in 111 genera, arranged in 5 famihes and dis- 

 tributed as follows: Stigmateaceae, 11 genera; Polystomellaceae, 

 39; Microthyriaceae, 36; Trichopeltaceae, 6; and Hemisphaeria- 

 ceae, 19. In the arrangement of Theissen and Sydow the families 

 are separated on the following bases: 



1. Fructification (shield) radially constructed 2 



2. Mycelium thread-like, either not abundant or else wanting 3 



3. Ascomata largely internal 4 



4. Ascomata subcuticular Stigmateaceae 



4. Ascomata superficial but hypostromata internal 



Polystomellaceae 



