230 CLASS ASCOMYCETEAE 



Order Pezizales : Suborder Inoperculatae. This suborder differs from 

 the Operculatae in the absence of an operculum. The apex of the ascus 

 is usually thicker and sometimes depressed. When the spores are mature 

 the ascus elongates and often becomes thicker by the increase in turgor 

 due to the absorption of water. The apical portion of the ascus softens 

 and thickens and finally gives way suddenly, permitting the violent 

 expulsion of the contained liquid and ascospores as the distended ascus 

 wall contracts. The apothecia vary greatly in size, structure, and con- 

 sistency. Nannfeldt (1932) divided the many genera and species into 

 three orders: Lecanorales (already discussed above), Ostropales, and 

 Helotiales. Because the life histories and inner apothecial structures are 

 llioroughly known in so few of the described species it seems best to the 

 author not to recognize the latter two orders of Nannfeldt until detailed 

 structural and developmental studies in the Lecanorales and in the 

 operculate and inoperculate Pezizales shall enable mycologists to set up 

 a more scientific classification of the whole group of Discomycetes. 



Family Ostropaceae. The members of this family are characterized 

 by the narrow elongated asci with thickened apex through which runs 

 a slender canal almost to the surface, and by the long, thread-like asco- 

 spores which are septate at frequent intervals and which break up at 

 maturity into cylindrical pieces. The excipulum is mainly pseudoparen- 

 chymatous. The apothecium may be stalked (Vibrissea), superficial 

 without stalk {Apostemidium) , sunk in the substratum and disk-shaped 

 (Stictis), or rarely perithecium-like, with an ostiole (Ostropa). Among the 

 families which would make up Nannfeldt's order Helotiales only a few 

 are mentioned: 



Family Dermateaceae (Including Mollisiaceae). Apothecia small 

 or medium sized, mostly epiphytic on woody or herbaceous plants, some- 

 times on the ground, parasitic or saprophytic, usually fleshy but some- 

 times cartilaginous or leathery, mostly not bright-colored. Excipulum 

 usually pseudoparenchymatous and dark-colored. The apothecia are 

 often formed within the host tissue, breaking out and opening at matur- 

 ity. Mollisia, however, produces its apothecium externally on the host 

 tissues. It has one-celled rather elongated ascospores. Pseudopeziza pro- 

 duces its apothecia out of a well-developed stroma under the epidermis 

 of the parasitized leaf which is ruptured at the maturity of the apo- 

 thecium. The ascospores are one-celled. Ps. medicaginis (Lib.) Sacc. is 

 sometimes the cause of yellowing of the foliage of alfalfa or lucerne 

 {Medicago saliva L.) and its premature leaf fall. Drepanopcziza rihis 

 (Kleb.) V. Hohn. {Ps. rihis Kleb.) produces its apothecia on dead leaves 

 of species of Ribes. The actively parasitic stage of this fungus produces 

 only the conidial type of reproduction formerly known as Gloeosporium 

 rihis (Lib.) Mont, and Desm. Diplocarpon likewise produces its apothecia 



