210 A MANUAL OF THE ASPERGILLI 



the same strain, and occasionally in the same head (fig. 60 C), ranging from 

 5/i in length in some cases to 15 or 20/t and even 30/x under other conditions, 

 commonly septate; secondary sterigmata usually uniform in all heads, 

 from 5 to 8/x by 2 to 2.5 or 3/x. Conidia colorless, globose or subglobose 

 in most strains to elliptical or barrel-form in others, thin-walled, 2.5 to 

 3.5ju or occasionally 4/x, smooth. 



Reddish-purple to black sclerotia, consisting of thick-walled, parenchyma- 

 like cells, occur in many strains (fig. 59 C). 



As there is no possibility of determining which of the white Aspergilli 

 was in Link's possession, the name is here used to cover a whole series of 

 strains which are found everywhere but are most frequent in the later 

 stages of decay in vegetation and are especially characteristic of moldy 

 grain. Included within the series as we consider it are two rather different 

 cultural entities. The first of these is characterized by thin colonies in 

 which the mycelium is largely submerged and only fruiting structures, 

 commonly arranged in concentric zones, rise above the level of the sub- 

 stratum (fig. 59 B). In other strains, colonies are rather floccose and some- 

 what felted and often attain a depth of 2 mm., with fruiting structures 

 arising from aerial as Well as submerged mycelia. Sclerotia, generally in 

 purple or black shades, regularly and consistently develop in many strains 

 including representatives of both of the above colony types. Conidiophores 

 vary greatly in size and characteristically reach their greatest dimensions 

 upon the drier portion of agar slants, or upon slightly moistened grain and 

 other comparable products low in water content. The sterigmata in 

 organisms of this group warrant particular attention since the two series 

 commonly, but not consistently, differ tremendously in size. In many 

 strains the primary sterigmata are characteristically wedge-shaped and 

 reach dimensions of 25 to 30m by 10 to 12/* (fig. 60 A and C) ; such structures 

 are commonly septate. In other heads from the same culture the primary 

 sterigmata may be relatively small and measure 6 to 8/x by 2.5 to 3. 5/i 

 (fig. 60 B). Secondary sterigmata are consistently small and of the dimen- 

 sions indicated in the species description. 



"White" Aspergilli regularly constitute a normal element in the micro- 

 population from moist or improperly dried grains and of comparatively 

 dry vegetation undergoing slow decay. From such material, many in- 

 vestigators have described molds characterized by white heads which 

 obviously belong in this group, but without supplying sufficient critical 

 data to permit subsequent verification of the exact types under study. 

 Some of these descriptions were based upon molds growing in culture; 

 more of them were not. A few of the more tangible of these probable 

 synonyms will be briefly considered in this connection ; others will be found in 

 the general species index (pp. 331-?). 



