MORPHOLOGY AND DESCRIPTION 11 



morphological picture most frequently encountered, rather than upon a 

 selected strain assumed to be, but not known to be, the one first described. 

 Descriptive terms: For purposes of description, a standardized use of 

 terms has been adopted. Great diversity is encountered in the literature 

 in various languages. Even translated into Latin, Saccardo never homo- 

 genized the terms so that succeeding descriptions upon the same page use 

 descriptive terms in the same sense. To make comparison with existing 

 literature more convenient, the usages defined in the following pages 

 will cover the morphology as definitely as possible and indicate the usages 

 found in the older literature. To serve as a basis for the collection, 

 interpretation, and presentation of pertinent information regarding 

 Aspergilli to be studied, a guide sheet of the type used by the authors is 

 presented in the introductory portion of the manual proper (p. 82). 



THE ASPERGILLUS COLONY 



Since few of the Aspergilli regularly produce perithecia and ascospores, 

 a basis for identifying the majority of the molds of this group as they are 

 actually encountered in nature and in culture must be found in the de- 

 scription of the colonies and in the details of morphology found in the spore- 

 bearing structures available. 



The vegetative mass of most Aspergilli consists of submerged mycelium 

 from which only fruiting hyphae rise above the surface. Such colonies 

 suggest a field of ripening grain, in which conidiophores and ripening heads 

 predominate, and have been described as velvety (the German term used 

 is rase) from their appearance in many species. Some species produce a 

 more or less aerial felt (floccosity) of branching and interlacing hyphae 

 bearing conidophores. This is characteristic of certain strains of the A. 

 versicolor and A. fumigatus groups upon Czapek's solution agar and other 

 culture media commonly employed, and it is normally one of the most 

 striking characters of A. wentii under laboratory cultivation (fig. 1 B). 

 Many strains of the A . glaucus group form long streamers of hyphae hanging 

 from meat stored in cool, damp rooms and certain of these retain this 

 character in laboratory culture. The character of the surface growth is 

 a diagnostic characteristic which is usually fairly reliable under reasonably 

 uniform conditions of culture. 



In describing the Aspergillus colony, cognizance should be taken of such 

 factors as age, rate of growth, temperature of incubation, and the composi- 

 tion of the substratum. Provided with this information, subsequent 

 investigators can intelligently interpret their cultures in terms of species 

 previously described. 



Many species and strains of Aspergillus often produce conspicuously 

 zonate colonies. Most commonly, these take the form of fairly regular 



