86 A MANUAL OF THE ASPERGILLI 



SPECIES KEYS 



No general or comprehensive key to the species of Aspergillus is pre- 

 sented. Instead, a series of comparatively simple species keys are included 

 in the discussions of the several groups. The recommended procedure in 

 identifying an Aspergillus with the aid of this manual is first to determine 

 its group relationship by means of one or more of the group keys presented 

 below, then assign the culture more precisely to species by means of the 

 intra-group species key for the particular group to which the form belongs. 



GROUP KEYS 



Three keys to the groups of Aspergilli are offered : The first is presented 

 in the form of a diagram and presents the different groups in what we con- 

 sider their natural order. Presentation of this key in graphic form, it is 

 believed, will materially assist the user in grasping the various characters 

 which ally and interrelate the different groups. Primary separation is 

 based upon the number of series of sterigmata, whether single or double. 

 Secondary separation is based upon the character of the conidiophore, 

 whether rough or smooth. Tertiary separations are based upon the 

 presence or absence of perithecia, hulle cells, and sclerotia, and upon 

 the color of the conidiophore wall. 



In assigning species to groups by means of this key, the transitional or 

 intermediate character of certain species becomes strikingly apparent. For 

 example, Aspergillus caespitosus possesses the brown conidiophore and 

 conidial coloration of A. nidulans, furthermore, it produces clusters of ir- 

 regular, thick-walled hulle cells; but the head is radiate, or only loosely 

 columnar, and no perithecia or ascospores are produced. It is placed in the 

 A. nidulans group with full recognition that it possesses certain characters 

 which relate it to A. ustus. Aspergillus alliaceus is another form with 

 intermediate characters. The conidiophore is uncolored and smooth when 

 examined in liquid mounts (appearing finely roughened when examined 

 dry), and the sclerotia are black, but the heads are essentially ochraceous 

 in color. It is placed in the A. wentii group but shows unmistakable re- 

 lationship to A. ochraceus. Aspergillus sparsus is a species of uncertain 

 relationship. It possesses a conspicuously roughened, yellow conidiophore 

 and globose head, and is placed in the A. ochraceus group; but the conidial 

 heads show a greenish color which is not found in any other known member 

 of this group, while the character of the conidiophore will not warrant place- 

 ment elsewhere. The so-called "bronze series" in the A. tamarii group 

 is transitional in the direction of A. flavus. Colonies are conspicuously 

 green when young and retain a greenish tint for a considerable period, in 

 contrast to A . tamarii which never shows true green and appears greenish 

 only transiently when young. Such a list of intermediate species and forms 



