136 RESEARCHES ON FUNGI 



misconception. A list of fungi in which intrahyphal hyphae have 

 been seen, compiled by Dodge in 1920, includes Alternaria, Botrytis 

 cinerea, Sclerotium hydrophilum, Dematium pullulans, Rhizoc- 

 tonia, Morchella esculenta, Oloeosporium nervisequum, and 

 Gymnosporangium . 



Intrahyphal hyphae can be found in old hanging-drop cultures 

 of both Pyronema confluens and Fimeiaria fimicola. Just as in 

 other similar fungi, the mycelium, as it grows older in an exhausted 

 medium, tends to concentrate its protoplasm in certain cells, thus 

 forming gemmae. Here and there in a hypha one or more cells 

 die. The remaining living cells then often produce slender hyphae 

 which grow through adjacent dead cells intrahyphally. These 

 new hyphae, by means of hyphal fusions, may then serve to re- 

 connect two older living cells which previously, owing to the death 

 of one or more intermediate cells, had become separated from one 

 another. It was found possible to cause new hyphae to grow out 

 from septa intrahyphally as a result of operating upon the older 

 hyphae of a mycelium. The production of intrahyphal hyphae 

 under experimental conditions will now be described. 



Some spores of Pyronema confluens were sown in a shallow drop 

 of cleared dung- agar. Two days later, when the mycelium had 

 spread across the drop, the pointed end of a beading needle was 

 drawn across the drop in the manner already described. Thereby 

 several of the main hyphae were cut into two parts. The end of 

 one part of one of the hyphae operated upon is shown in Fig. 70, A. 

 As usual, each septum between a living and a dead cell became 

 pressed forward convexly into the dead cell and its pore plugged 

 (cf. Figs. 67 and 68). These convexo-concave septa remained un- 

 changed for about half an hour and then from the side or middle 

 of some of them, as shown semi-diagrammatically in Fig. 69 (p. 135) 

 and in an actual case in Fig. 70, B, a new and relatively slender 

 hypha began to push its way forward within the cavity enclosed 

 by the collapsed and cylindrical wall of the dead cell. The new 

 hyphae grew rapidly in length, and the one illustrated in Fig. 70 

 attained the length represented at C about two and one-half hours 

 after the hypha had been severed. The new hyphae frequently 

 branched and formed hyphal fusions with other hyphae. 



