THALLOPHYTES 
73 
mg filaments (ascogenous hyphae), whose ultimate branches form asci. 
This fertilized oogonium giving rise to ascogenous hyphae is usually 
called an ascogonium. From hyphae beneath the ascogonium branching 
filaments arise that produce the colored paraphyses, and still other 
sterile hyphae give rise to the ascocarp (fig. 178). Usually several 
ascogonia are involved in a single ascocarp. 
FIG. 177. Pyronema: oogo- 
nium with its conjugating tube (or 
trichogyne) ; antheridium curved 
around the trichogyne (hence in 
section the latter appears as if 
piercing the former) ; trichogyne 
tip fused with antheridium and 
receiving nuclei; nuclei collecting 
in oogonium. After HARPER. 
FIG. 178. Pyronema: somewhat diagram- 
matic section of an ascocarp (involving two 
ascogonia), showing ascogenous hyphae aris- 
ing from the fertilized oogonium (ascogonium) 
and producing asci. After HARPER. 
Ascobolus. In this form structures resembling sex organs have 
been found, and may be interpreted with the help of the life history of 
Pyronema. From the mycelium there arises a large, bow-form, septate 
hypha (the "swollen hypha "), to which other slender branches become 
attached. No fusion has been observed, but the position of the slender 
branches suggests that their function may be that of antheridia. In 
any event, the septate swollen hypha becomes a single chamber by the 
disappearance of the cross walls, and then gives rise to ascogenous 
hyphae that bear the asci. The paraphyses and the ascocarp also 
arise in the way described for Pyronema. It seems safe to infer that the 
