Dodge: Life History of Ascobolus magnificus 125 



Intrahyphal Mycelium 



In old plate cultures it is not difficult to find internal hyphae 

 running back and forth, in and out of the larger hyphae (PI. 8, 

 fig. 2 and Text fig. 20) . Papulospores sometimes arise directly 

 from branches growing out of these internal hyphae. It is only 

 recently that I have been able to prove positively that this is not 

 a case of parasitism of Papulospora on Ascobolus. On the con- 

 trary, it is simply a good example of what has been described 

 under various names, such as Durchwachsungen, cordon interne, 

 accroissement perforant, etc. In old cultures of certain fungi, 

 one can find where bridging hyphae grow out from living cells 

 through dead ones (PI. 8, figs. 1, 3, 4), and connect up with the 

 next living cells. It is said that a new wall may be formed about 

 the reduced cytoplasm of an old cell, thereby constructing a new 

 hypha of a shorter diameter which occupies only a small portion 

 of the old cell cavity (31). It may happen that for long dis- 

 tances the cells of the hyphae degenerate so that the bud that 

 grows out to bridge the gap must pierce many cross walls (PI. 

 8, fig. 2 and Text fig. 19). We thus have what looks like the 

 intrahyphal mycelium of a fungus parasite or a case where a 

 fungus is parasitic on itself. The cross walls of the internal 

 hyphae do not in any way correspond to those of the outer 

 hypha whose septa not infrequently become almost invisible. 

 Sometimes the internal hypha, unable to penetrate the cross 

 wall at the first point of contact, runs along the wall to the other 

 side where it may be able to push through, if not it returns 

 through the same old cell and winds about several times before 

 growing out into the medium. There is usually a swelling on 

 the internal hypha where it passes through a septum of the big 

 cell. De Bary describes Cicinnobolus as an intrahyphal parasite 

 of the powdery mildews. Many persons who have investigated 

 the subject of Durchwachsungen have remarked on the close re- 

 in old cultures on a dung decoction agar. 24, 26. Surface views of heavy- 

 walled brownish cells surrounded by entangling hyphae. 25. Young papulo- 

 spore that will eventually possess three central storage cells. 27, 28. Chlamydo- 

 spore-like storage cells, papulospores?. 



