ASCOMYCETES (p. 64) 



2, 7, 19, 25, 46, S2, 53, 62 



The distinguishing mark of this group is the ascus. This in its 

 typical form is shown in Fig. 73, as a long, slender or club-shaped 

 sac in which the spores are borne. The number of spores in the 

 ascus is usually definite and is commonly of the series, 1, 2, 4, 8, 

 16, 32, 64, etc., the most common number being 8. The spores 

 vary in size, color, shape, markings and septation. The asci 

 in most genera are arranged in a definite group, a layer, con- 

 stituting the hymenium which may be either 

 concave, convex, or flat. Between the asci in the 

 hymenium are often found slender hyphal threads 

 of various form, the paraphyses, Fig. 73. 



The hymenium may be borne in or upon a 

 firm substratum of woven threads, the stroma, 

 or upon a very tenuous substratum, the subicu- 

 lum, or without any definite subascal structure. 

 The stromata vary widely in character, size, tex- 

 ture, color, surface, form, etc. 



The mycelium is usually abundant, branched 

 and septate, the septation readily distinguishing 

 this group from the Phycomycetes. In many 

 species the mycelium weaves together into a false 

 parenchyma and constitutes relatively large -p^^ 73. — Portion 

 spore-bearing structures. Fig. 74. "L^ing'ScTa'iS 



The ascigerous organ, ascocarp, or ascoma, paraphyses. Af- 



, , , . ii. • ter Chamberlain. 



if saucer-shaped and open is an apotbecium, 



Fig. 92; if closed a perithecium, Fig. 144. In other cases, the 



ascigerous layer covers the exterior surface. Fig. 74. 



On the boundary lines between the Ascomycetes and other groups 

 are fungi which do not present the typical Ascomycete picture 

 but which are regarded as probably belonging to the group, i. e., 

 transition forms between this and other groups. Among such are 



113 



