140 



COMPARATIVE MORPHOLOGY OF FUNGI 



and consist of long, narrow cells which are multinucleate (up to 15) in the 

 neighborhood of the growing tip (Fig. 85, 1). In the older part, however, 

 they are uninucleate by septation. Approximately 5 days after sowing in 

 artificial culture, two cells form copulation branches in the region of their 

 septa (Fig. 85, 2). The copulation branches do not always arise simul- 

 taneously, however, and their length is often unequal; also, both proc- 

 esses may not arise from neighboring cells but from cells separated by a 

 small, intermediate sterile cell. If they are not too short, they make a 

 half to complete turn about each other. In Eremascus albus (Eidam, 

 1883a), they coil helically (Fig. 86). 



Their tips touch, the walls at the point of contact are dissolved, 

 and the two copulation branches come into open communication. The 



M 



Fig. 85. — Eremascus fertilis. Development of asci. (X500; after Guillermond, 1909.) 



nucleus of the hyphal cell divides; one daughter nucleus remains behind 

 in the hyphal cell, the other wanders out into the copulation branch, 

 and fuses there with the nucleus of the other branch (Fig. 85, 4 to 8), 

 The zygote (the bend of the copulation bridge) swells up to an ascus, 

 which is ab jointed from the copulation branches; its nucleus divides 

 thrice and the eight spores are surrounded by a double membrane (Fig. 

 85, 9 and 10); occasionally some spores remain behind in development 

 and degenerate. 



The spores are liberated by disintegration of the asci. At germina- 

 tion the spores swell to twice the size, rupture the exospore to form 

 one or more germ tubes which, after repeated nuclear division, develop 

 to hyphae. 



In addition to this normal development, cases of parthenogenesis 

 occur occasionally; two copulation branches may swell to asci without 

 copulation; similarly, a copulation branch which finds no partner may 

 develop independently (Fig. 85, 11); besides, especially in old cultures, 



