KEY TO THE ORDERS OF OSTIOLATE "PYRENOMYCETES" 299 



lution of the intervening septa reach the oogone cell. Subsequently asco- 

 genous hyphae are produced. Pleospora has dark-colored muriform asco- 

 spores. In some species the conidia belong to the form genus Stemphylium 

 in which the muriform conidia are produced singly and in other species 

 the conidia are produced in acropetal chains belonging to the form genus 

 Alternaria. 



Family Botryosphaeriaceae. Probably also to be included in the 

 Order Pseudosphaeriales are the families Botryosphaeriaceae and Cucur- 

 bitariaceae. These differ from the foregoing families by possessing a more 

 massive stromatic ascocarp. The ascocarps of these two families possess a 

 subcortical hypostroma the upper part of which bursts through the bark 

 and develops as a more or less spherical, perithecium-like body. In the 

 Botryosphaeriaceae the thick wall has a thin blackened and carbonaceous 

 outer layer and the asci are broadly clavate. 



Family Cucurbitariaceae. In this family the main portion of the 

 stroma, the hypostroma, is well developed or consists of a limited mass of 

 mycelium intermingled with the remnants of the host tissue. From the 

 surface of this basal stroma there bulge out numerous, crowded, more or 

 less spherical stromatal projections or pseudoperithecia in which the 

 development of asci occurs without the production of true paraphyses. 

 These ascocarps have thinner walls than those of the foregoing family, 

 with a thinner blackened outer layer. Most members of the family are 

 saprophytic on wood and bark but possibly some are parasitic. In some 

 species conidia are produced in pycnidia. Cucurhitaria is the largest and 

 most frequently observed genus. It is placed by Theissen and Sydow 

 (1916) in this order. 



The relationships and phylogeny of the orders considered in this 

 chapter are not at all certain. Theissen and Sydow, Gaumann (1928), and 

 Petrak (1923) would derive the Sphaeriales from the Pseudosphaeriales 

 which in turn they would derive from the Myriangiales and these from 

 near the Aspergillales. The author is inclined to consider that the simpler 

 forms of Sphaeriales and Hypocreales, with hyaline or light-colored, one- 

 celled ascospores and a definite hymenial layer are the more primitive and 

 that from these have arisen the other orders. This will be discussed more 

 fully in Chapter 17. 



Key to the Orders of Ostiolate "Pyrenomycetes" 



Ascocarps are true perithecia with or without marked stromatic outei- layer or 

 surrounding stromatic tissues. Periphyses and true ostioles usually present. 

 True paraphyses present or early disappearing, in some cases apparently 

 entirely lacking. 

 Perithecia with dark-colored, usually firm walls. Not lichen forming. 



Order Sphaeriales 

 Perithecia dark-colored. Lichen forming. Order Pyrenulales 



