IV] 



PEZIZALES 



121 



multicellular archicarps, each rather like the single scolecite of Ascobolus. 

 The cells are not connected by pores, and ascogenous hyphae arise from 

 several in each archicarp. 



In R. brunneus Dangeard reports a single archicarp, consisting of a short, 

 somewhat twisted branch. Ramlow has also recorded a single archicarp in 

 R. polysporus and Barker in an unnamed species. Overton has made some 

 study of the development of the numerous spores in R. Pelletieri. The 

 ascus nucleus divides as usual to form eight free nuclei, these undergo a 

 period of rest and growth and then divide further till thirty-two free nuclei 

 are formed. Around these the spores are delimited in the usual way. 



Thelebolus stercoreus has a mycelium of uninucleate cells, from one of 

 which the archicarp arises as a thick branch containing a single nucleus. 

 Later two, four, and finally eight, are seen (fig. 85), and then septation takes 



Fig. 



^ - -_' 



B4. Thelebolus stercoreus Tde. ; a. young ascocarp with binucleate asci ; b. ascus 

 containing fusion nucleus, both x 810 ; after Ramlow. 



place, so that a row of cells is formed. Most of these are uninucleate, but 

 one contains two nuclei (fig. 84^); it enlarges and becomes the single ascus ; 

 in it the two nuclei fuse (fig. 84^). The definitive nucleus divides karyo- 

 kinetically, sometimes as many as ten times, so that 1042 nuclei are formed. 



Fig. 85. Thelebolus stercoreus, Tde.; development of archicarp, x 1750; after Ramlow. 



Spore-formation takes place apparently in the usual way. The wall of the 

 ripe ascus is about 2/* thick, but a thinner region is present at the apex, sc 

 that a concave papilla is differentiated, which is concerned in the dehiscence 

 of the ascus. A sheath of vegetative hyphae grows up from the surrounding 



cells. 



