38 



ASCOMYCETES 



[CH. 



fresh asci reach maturity is necessary before the phenomenon can be 

 repeated. 



The Ascocarp. In a few genera, asci are developed singly on the 

 mycelium, but in the great majority of cases they arise in closely associated 



groups, and are surrounded 

 by a protective wall or peri- 

 dium of sterile filaments so 

 that a definite fructifica- 

 tion, the ascocarp or asco- 

 phore, is formed. This 

 structure is usually more or 

 less spherical and com- 

 pletely closed in the young 

 stages; it may retain this 

 form at maturity, opening 

 only by the decay or irregu- 

 lar splitting of its walls, it 

 may assume a flask-shaped 

 outline and open by a ter- 

 minal poreorostiole(fig.6), 

 or it may spread out to form 

 a cup in the concavity of 

 which the asci are fully ex- 

 posed (fig. 7). To the closed 

 or flask- shaped forms the 

 term perithecium is ap- 

 plied, the cup and its vari- 

 ants are known as apo- 

 thecia. Inthesimplerasco- 

 carps the asci are irregu- 

 larly scattered", in the apo- 

 thecia and flask-shaped perithecia they are regularly arranged, forming a 

 more or less parallel series and intermingled with paraphyses. 



The Paraphyses. The paraphyses of the Ascomycetes are slender hairs, 

 of about the same length as the asci; they usually develop earlier than the 

 latter, and have a protective and possibly a nutritive function ; in the 

 simpler ascocarps their place is taken by the inner layers of the sheath. 

 The paraphyses are often clavate or club-shaped in form with a rather 

 swollen tip (fig. S), sometimes cylindrical (fig. 4) or pointed (lanceolate), 

 or sometimes with curled or twisted ends; they may be simple or branched, 

 septate or continuous, hyaline or provided with coloured contents ; orange 

 red granules are common and often give a brilliant tinge to the whole 



Fig. 6. Sordaria sp. ; ascocarp in longitudinal section 

 showing asci, paraphyses and periphyses ; x 400. 



