28 A MANUAL OF THE PENICILLIA 



Hence, it is necessary to treat the preparation with a solvent such as 

 ethyl alcohol prior to the addition of water or some mounting fluid. Water 

 is satisfactory if observations can be completed within a few minutes. If 

 the preparation is to be retained for several hours or .even days for com- 

 parative examination with other specimens, some type of non-drying 

 mounting fluid must be used. Weak glycerine (10-20%), with or without 

 the addition of a stain such as eosin, can be used over a considerable period; 

 and if allowed to concentrate, can be sealed to form a semi-permanent 

 preparation. It has become routine practice in our Laboratory to wash 

 preparations quickly in 70% alcohol and then mount in a fluid such as 

 Amman's mounting fluid which neither plasmolyzes, swells, nor discolors 

 the cells of most Penicillia. The composition of this mounting fluid, 

 which was developed about 1896, is as foflows: 



Carbolic acid crystals (c.p.) 20.0 gms. 



Lactic acid (sp. gr. 1.2) 20.0 gms. 



Glycerine (sp. gr. 1.25) 40.0 gms. 



Distilled water 20.0 ml. 



The carbolic acid crystals are first liquefied by heating in a water bath. 



CuLTUiL\L Characteristics 



COLOR OF CONIDIAL AREAS 



Every description of a Penicillium emphasizes some color, or series of 

 colors, as characteristic of conidial areas. If the describer uses several 

 culture media, it is usually necessary to specify the color upon each by 

 name or numerical reference in some of the recognized color standards. 

 Our own records over a period of many years, including the current study, 

 are based upon Ridgway's "Color Standards and Nomenclature" published 

 in 1912. Much of the European literature is based upon Klincksieck and 

 Valette's "Code des Couleurs" published in 1901. As yet no one has 

 adopted the newer color manuals such as the "Munsell Book of Color" 

 in which a greater number of hues and values are available for citation. 

 Reference to such manuals will undoubtedly become necessary in the fu- 

 ture since both Ridgway's and lOincksieck and Valette's works are out of 

 print and no longer generally available. Illman and Hamly (1948), at the 

 University of Toronto, are currently establishing the identity of Ridgway's 

 color chips with specific color notations in Munsell's atlas. 



Our records show considerable variation in color for particular strains 

 as interpreted by diff"erent individuals, or by the same individual working 

 at difi'erent times. For this reason, citation of color is never an absolute 

 guide even though a particular shade is designated. In general, however, 

 the colors produced by a given strain of Penicillium upon a standardized 



