Chapter VIII 

 THE ASPERGILLUS CLAVATUS GROUP 



Outstanding Characters 



Conidial heads clavate 1 , large, pale blue-green. 

 Conidiophores generally coarse, smooth-walled, uncolored. 

 Sterigmata in one series. 

 Conidia elliptical, smooth, comparatively thick-walled. 



Group Key 



Conidial structures not exceeding 4.0 mm. in length. 



Aspergillus clavatus Desm. 

 Conidial structures often 1 to 5 or more cm. in length. 



Aspergillus giganteus Wehmer. 



Aspergillus clavatus Desmazieres, in Ann. Sci. Nat. Bot. (2) 2: 71, p. 2, 



fig. 4. 1834. 



Colonies upon Czapek's solution agar growing rapidly at 20-24° C, 

 plane or slightly furrowed, in certain strains tending to become floccose 

 but generally characterized by a surface mycelial mat and abundant erect 

 conidiophores up to 3.0 mm. in length, bearing large, blue-green, clavate 

 conidial heads evenly distributed or arranged in more or less well defined 

 zones (PI. Ill, A and Fig. 21 A); reverse generally uncolored, but becoming 

 browned in age in some strains; odor strongly foetid in some strains, not 

 pronounced in others. Conidial heads clavate, large, commonly ranging 

 from 300 to 400m by 150 to 200m, in age splitting into 2, 3, or more divergent 

 columns of compacted conidial chains (Fig. 21 B), approximately slate- 

 olive in color (Ridgway, PI. XLVII). Conidiophores 1.5-3.0 mm. in 

 length, 20 to 30m in diameter, comparatively thin-walled, smooth, color- 

 less, gradually enlarging at the apex into a clavate vesicle which is fertile 

 over an area up to 200 to 250m in length and 40 to 60m or more wide (Fig. 

 21 C). Sterigmata in a single series, varying in size from 2.5 to 3.5m by 

 2.0 to 3.0m at the base of the vesicle to 7.0 or 8.0 and occasionally 10m by 

 2.5 to 3.0m at its apex (Fig. 21 D). Conidia elliptical, comparatively 



1 Aspergillus janus Raper and Thorn (see page 187) is characterized by a smaller 

 clavate vesicle in one of its conidial phases. It is hardly to be confused with the 

 clavatus group, however, because of the whiteness of its conidial masses, the double 

 series of sterigmata, and the intermixture of more or less abundant green A. sydowi- 

 like heads in cultures at room temperature. 



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