107 



aerial mycelium of some races produced clumps (PI. XIII, XXII, XXIII), 

 which under the microscope are seen to be due to a peculiar distortion and 

 abundance of the aerial mycelial tips (Fig. 6, d). This peculiar behavior 

 of the terminal parts of the mycelium shows some similarity to the branch- 

 ing figured by Ward (123) in Botrytis in the early stages of development of 

 attachment organs. Anastomosis is very common with this fungus (Fig. 

 5, a and b), and Ward (123, fig. 19) has figured anastomosis of very similar 

 character for Botrytis. Many citations of its occurrence are given by 

 Beauverie and Guilliermond (13). (See also their figures 4 and 8.) 



The nuclei in the mycelium are extremely small, but may be seen readily 

 when stained with gentian violet, and still better if stained with iron-hae- 

 matoxylin. They vary in number, but are never less than two and usually 

 more; they do not typically group in pairs; and they are irregularly dis- 

 tributed in the protoplast. Nuclei apparently in mitosis are frequently 

 seen, but since they are so small no details were noted except that the 

 mitoses of all of the nuclei in one cell seem to be simultaneous, and mitosis 

 was probable in adjacent cells. Reports on the nuclear conditions in the 

 fungi imperfecti are few and unsatisfactory, doubtless owing to the extreme 

 difficulty of the subject. Dangeard (39) notes nuclei and mitosis in the 

 rather anomalous genus Bactridium; Beauverie and Guilliermond (13) in 

 Botrytis; while Higgins (66) gives quite satisfactory figures for Mycosphae- 

 rella. 



Senescence phenomena of aerial mycelium (Fig. 7, a b). When the 

 aerial mycelium is young it constitutes a more or less abundant, loose, 

 arachnoid, fluffy mass. In quite old cultures it is observed to mat down 

 close to the surface of the medium in a thin, glazed, dead layer. Inter- 

 mediate between these two extreme conditions interesting phenomena 

 occur. The first observable change from that of the normal, vigorous 

 mycelium is that certain cells of a filament, often many adjacent cells, be- 

 come nearly or quite devoid of protoplasm (Fig. 7, i, o, and g] , though cells 

 at each end of such a series still appear normal (see i and j). Quite fre- 

 quently the fungus re-grows from a protoplasmic cell, through the empty 

 threads, as is shown in n and o. In other instances, and much more com- 

 monly, the empty cells gradually collapse until they remain as very 

 thin, smooth filaments (c, h, and m), apparently of gelatinous texture. 

 Where two filaments undergoing such dissolution cross they blend (a, b, 

 m) ; and where several meet, rather large amorphous unorganized masses 

 are seen, superficially much resembling a plasmodial structure (a). There 

 was, indeed, at first, suspicion that there might be present a plasmodial 



