22 A MANUAL OF THE ASPERGILLI 



with low magnification, often rough or echinulate (e.g., A. flavus-oryzae 

 group). The secondary thickenings in such conidiophores appear to have 

 been laid down around protoplasmic areas, which, for a time at least, 

 maintain contact with the primary wall outside. The size and abundance 

 of the pits in the mature conidiophore wall differ with the species, but in a 

 general way correspond with the rate of withdrawal of the protoplasmic 

 mass from its primitive connection with the original outer wall. In some of 

 the species in both groups, warts, or superficial and usually more or less 

 hemispherical concretions are found on the outer surfaces of the conidiophore 

 wall, sometimes few and scattered widely, again fairly numerous, but always 

 unevenly distributed (e.g., A. ochraceus group). These warts, or con- 

 cretions, appear to be deposits of excreted substance, possibly due to the 

 evaporation of the numerous drops or globules of liquid abundantly visible 

 upon the young and growing conidiophores. 



The color of the conidiophore wall may be homogeneous, or the layers 

 may differ markedly in shade. In a number of the groups the entire 

 wall is hyaline. In certain other groups the outer layer is yellow as in 

 A. ochraceus and A. fiavipes, or it may be some shade of green, brown, or 

 avellaneous. In some species the whole wall is colored for all or part of 

 its length. No explanation of these color differences is available, except 

 possibly the varying concentration of aspergilline (Linossier, 1891) in the 

 upper part of the conidiophores of members of the A. niger group, as well as 

 in the conidial heads. 



The Vesicle 



The conidiophore is usually much larger toward the apex than at the 

 point of origin. At the base of the head a further dilation occurs more or 

 less abruptly to produce the vesicle (blase, of the German mycologists). 

 This vesicle is globose, hemispherical, elliptical, or long clavate in various 

 groups of the Aspergilli and furnishes an enlarged surface for the attachment 

 of spore-bearing cells. The lumen of the vesicle is continuous with that 

 of the upper part of the conidiophore; a septum near the base of the head 

 is occasionally, but only rarely, seen (see Corda, A. mucoroides for descrip- 

 tion), and has not been regularly found in any species. 



Sterigmata (Compare Fig. 3) 



The conidia-bearing surface, represented by the fertile area of the vesicle, 

 is closely covered by the simultaneous development of a layer of cells, the 

 sterigmata, each in a general way perpendicular to a point on the fertile 

 surface of the vesicle. In figure 3A a single layer of such cells is shown, 

 each of which produces an unbranched chain of conidia. In figure 3B 

 each of the first series of cells, or primary sterigmata, bears two to several 



