MORPHOLOGY AND DESCRIPTION 15 



series as .4. fumigatus, A. nidulans, and A. ochraceus, however, strains or 

 races may be found which vary from conidial walls smooth or nearly so, 

 to walls bearing echinulations or even traceries apparently produced by 

 aggregation of color substance into spinules, or bars between the outer 

 and inner walls of the cells. Although smoothness and echinulation have 

 received much weight in descriptive literature, observations such as the 

 above would indicate that this character should only be used to separate 

 nearly related strains in the same group, rather than as a group character. 

 Literature on the nature of color in Aspergilli seems to begin with 

 Linossier's study of aspergilline as produced by A. niger in 1891; this was 

 followed more recently by Quilico, and Quilico and Di Capua in 1933. 

 Disregarding the record of observations only, more pretentious work 

 appeared when Bainier and Sartory undertook to use color production to 

 separate members of the A. glaucus group about 1910 to 1912. Their 

 experiments supplemented observations of colonies checked against a 

 color chart, with a routine series of solubility and precipitation tests. 

 Blochwitz (1929-1935) followed by using a series of routine solubility tests 

 against all species producing bright colors but failed to coordinate his 

 tests to show the relation of test to culture medium and conditions and to 

 age of the culture studied. Later Gould and Raistrick (1934) and Raistrick, 

 Robinson, and Todd (1937) studying the A. glaucus group, extracted and 

 defined the colors found, but again failed to follow the transformations 

 in the color of the particular species during the course of colony development. 

 Until someone correlates color determination and composition more 

 closely, color observations will continue to be useful accessory data which 

 must be related to the age of the colony and to the composition of the 

 medium as closely as possible to have value. 



Colors in the Substratum 



Production of bright colors in the substratum is frequent among the 

 Aspergilli. The color produced by any species or race in any medium is 

 dependent first on the ability of the mold to elaborate the particular 

 product, and second on the presence of the necessary building material 

 in the substratum. A mold may grow well upon a particular medium 

 without discoloring it; a transfer from this colony to another substratum 

 may turn the second medium red or yellow. 



Color in the substratum is the result of the particular Aspergillus acting 

 upon the particular medium under a certain range of temperature. Most 

 of the species of Aspergillus, if they produce any color, produce from a 

 trace to abundant yellow in the early stages. This may persist, or give 

 place to shades of orange, red, or purple. In some cases, the color fades 

 out as the colony becomes older. In descriptive work, progressive changes 



