48 A MANUAL OF THE ASPERGILLI 



satisfactory, however, to use some mounting fluid of a composition designed 

 neither to swell nor plasmolyze the tissues to be observed. Such a 

 mounting fluid was developed by Amann as early as 1896 and has been 

 used by mycologists, quite generally, for many years. Its composition 

 is as follows: 



Carbolic Acid Crystals (c.p.) 20.0 grams 



Lactic Acid (sp. gr. 1.2) 20.0 grams 



Glycerine (sp. gr. 1.25) 40.0 grams 



Distilled water 20.0 cc. 



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



The mounting fluid is normally used without the addition of any dye, since 

 in the diagnosis of the Aspergilli the natural colors of conidiophores, conidia, 

 etc., are very important. If it is considered desirable to stain the tissues 

 under observation, it is possible to incorporate into the lactophenol solution 

 some coloring substance such as cotton blue, eosin, or some other aniline 

 dye. In making mounts of the Aspergilli, it is profitable to wet the material 

 first with 70 percent alcohol to drive off air bubbles, and then quickly add a 

 small drop of the lactophenol prior to the placement of the cover glass. 



Incubators 



Almost all of the Aspergilli grow well and sporulate abundantly at 

 laboratory temperature. There are, however, certain exceptions to this 

 general rule (see p. 45), and for this reason it is desirable to have available 

 an incubator which can be regulated at temperatures below that of the 

 laboratory and others covering different ranges up to 37° C, or even 50° C. 

 The type of incubator is not critical and almost any type of cupboard, or 

 room, will prove satisfactory if the temperature can be controlled to 

 within 1° C. ±, and if the air is neither excessively dry nor humid to the 

 point where cotton plugs become moist upon continued exposure. 



Microscopes 



In the study and identification of Aspergilli it is essential to have at one's 

 disposal a good-quality compound microscope. If possible, this should be 

 provided with apochromatic lenses. In our experience we have found a 3 

 mm. objective used in conjunction with either 10 X or 15 X oculars to give 

 us magnifications and a degree of definition which is most satisfactory for 

 the examination of conidial structures. While it is not absolutely neces- 

 sary, it is desirable to have, in addition, a low-power, wide-field dissecting 

 microscope covering magnifications from 10 to 40 diameters. In the ab- 

 sence of such a microscope a high-quality pocket magnifier provides a good 

 substitute. 



