SPHAERIALES 



279 



die. At the same time the head again grows upward from below, by a 

 meristematic layer at its base, 8 or 9 cell layers thick. 



Meanwhile the plectenchymatic fungus tissue has spread into the bark 

 parenchyma lying under the plectenchyma disk. There it forces the 

 cell elements apart and, by gradual resorption of their bark cells, forms a 

 comparatively thick plectenchyma, the later entostroma (hypostroma, 

 Fuisting, 1867). In it the perithecia are formed nearly on a level within 

 the spherical hyphal knots. In each lies an ascogonium without trich- 



Per.- 



Fig. 184. — Diatrypc disciformis. 1. Section of fundament of ectostroma. Above the 

 peridium, Per; in the middle ectostroma, Ect, and below the bark parenchyma, Rp. 2. 

 Older stage. The central portion of the ectostroma is already verruciform while the 

 peripheral portion (right) is still forming conidia. Kon, conidial stroma. 3. Section 

 through ectostroma and entostroma, the latter has already formed perithecia. 4. Dia- 

 grammatic section through a mature fructification. The ectostroma, Ect, has already 

 separated; PI, placodium. (1, 3 X 400, 2 X 270; after Ruhland, 1900.) 



ogyne (Fig. 184, 3), from which the ascogenous hyphae are formed in an 

 unknown manner. 



The distal outer layer of the entostroma subsequently changes into a 

 horny sclerotic rind which is only interrupted by the perithecial necks. 

 Thereby the connection with the ectostroma is loosened, the latter is 

 thrown off, and the mature perithecial entostroma lies free in the ruptured 

 periderm. This horny, sclerotic rind layer, surrounding the perithecial 

 mouths, is called a shield or placodium (Fig. 184, 4). 



One of the causes of great confusion in the systematic literature of 

 the Sphaeriales is that the development of the stroma in the higher forms 



