CHAPTER XXI 

 PHACIDIALES 



The Phacidiales are connected on one side to the Hysteriales, on the 

 other side to the Dermateaceae and Bulgariaceae, in the Pezizales. In 

 time they will probably be divided between these two groups. They are 

 Discomycetes with ingrown or superficial perithecia, surrounded or 

 only developed above, rupturing at maturity by several irregular slits 

 above. According to one's definition and personal viewpoint, they may 

 be divided in different ways. Lindau (1897) divides them into three 

 families: the Stictidaceae, with slightly fleshy, bright-colored perithecia 

 and Tryblidiaceae and Phacideaceae with black leathery or carbona- 

 ceous, perithecia, which in the former possess a thick hypothecium and 

 project above the substrate; the latter, having only a thin, poorly 

 developed hypothecium, remain immersed in the substrate or in their 

 stroma. Hoehnel (1917) divided the order in the narrower sense into 

 six families based on the situation of the fructifications in the host tissue: 

 the Schizothyriaceae with flat fructifications upon the cuticle, the Lepto- 

 peltinaceae with subcuticular fructifications, the Dermopeltinaceae 

 with intraepidermal fructifications, the Phacidiaceae with subepidermal 

 or still deeper fructifications, the Phacidiostromataceae whose fructifica- 

 tions include the whole tissue between the epidermal layers of leaves, 

 coalesce with them or (in ramicolous forms) are sunk deep in the stem 

 tissues and here coalesce with the stem epidermis, and the Cryptomycet- 

 aceae with fructifications under the periderm of stems and twigs. 



The ontogeny of Cryytomyces Pteridis (Killian, 1918) and Rhytisma 

 acerinum (Jones, 1925) is known. C. Pteridis, causing a leaf roll of the 

 brake, belongs to the Phacidiaceae of Lindau's treatment, to the Crypto- 

 mycetaceae of Hoehnel's. At the beginning of the warm spring rains, 

 the ascospores of the over-wintered fructification infect the young fronds 

 of Pteris. At first the hyphae grow intercellularly, then intracellularly 

 in all directions and intertwine in the hypostomatal cavities to flat 

 cushions whose apical cells cut off fusiform, uninucleate conidia (Figs. 

 205 and 206). Conidial formation continues until the beginning of cold 

 weather. A protective layer is formed, changing the cushions to flat, 

 irregular pycnia. 



During the summer the fundaments of the ascus fructification are 

 formed as small plectenchymatic knots in the hypostomatal cavity. 

 The cells of the plectenchyma lying between the guard cells have a 



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