70 A MANUAL OF THE ASPERGILLI 



which 25 were either described as new species or new combinations. His 

 findings in A. niger are fairly illustrative of the same type of study in other 

 groups (compare Thorn and Currie [1916] for A. niger; Thorn and Church 

 [1921] for A. flams. 



Mosseray based his primary separations upon conidial sizes, shapes, and 

 markings, while secondary and tertiary separations were based upon co- 

 nidiophore lengths and the characters of colonies in tube cultures on 

 Biourge's "Raulin-neutre gelose" — a variation of the classic Raulin solution. 

 Biourge and Simonart demonstrated the entire series to one of us (C. T.) 

 showing how wrinkling and granulation of mycelium, intensity and changes 

 of secreted color, shades of color in the conidial area, lengths and propor- 

 tions of conidiophores and heads, and their distribution over the mycelium 

 gave to each strain an individuality which had been repeated in successive 

 cultures over a considerable time. We raised just one question, "What 

 would you do with the next thousand?" 



The large majority of all isolations of black Aspergilli conform within a 

 range of minor variation with the general van Tieghem concept, — i.e., 

 black-brown colonies with conidiophores and heads giving the general 

 structure and measurement of parts found in the classical description. 

 Then, in contrast with these, there are shades of colony color from the coal 

 black of A . carbonarius through shades of purplish-black to the brown of A . 

 ferrugineus Fuckel or to the lighter shades of Schiemann's mutants (pp. 

 223-224) . Some of them produce no colors in the substratum and reverse 

 of the colony; some show yellow in traces; others are persistently deep 

 orange, giving the whole a yellowish appearance. Or, again, the agar and 

 mycelium may develop a red-brown or "mauve" shade of violet. 



Conidiophores in the usual type of culture reach nearly enough the same 

 length to give the effect of a field of grain. But their length may be quite 

 short and the heads seem to be borne directly on the substratum, or they may 

 be several millimeters in length with the heads borne well above the sub- 

 stratum and correspondingly large. Between these extremes, every varia- 

 tion can be found. Conidiophores may be scattered thinly over the 

 vegetative mycelium, collected in a zone at the border, or crowded in 

 the center. 



The vegetative mycelium may grow as a flat felt (plane) or may be vari- 

 ously wrinkled, sulcate, or buckled. In a smooth or plane colony the 

 mycelial cells seem to stop growing early — the colony extends only at the 

 margin. In the plane colony intercalary growth (i.e., the formation of new 

 cells in the filament, or the lengthening of the old cells), and the production 

 of new branching ceases. Such mycelia ordinarily produce one crop of 

 conidial heads, beginning at the center of the colony and progressively 

 developing toward the margin until the medium is exhausted or some 

 inhibiting factor paralyzes growth. Marginal growth in such a colony 



