112 MICROBIOLOGY 



6. Optical characters (after Shuttleworth). 

 Transparent: transmitting light. 

 Vitreous: transparent and colorless. 



Oleaginous: transparent and yellow; olive to linseed oil colored. 

 Resinous: transparent and brown, varnish or resin colored. 

 Translucent: faintly transparent. 

 Porcelaneous : translucent and white. 

 Opalescent: translucent, grayish white by reflected light, smoky 



brown by transmitted light. 



Nacreous: translucent, grayish white, with pearly luster. 

 Sebaceous: translucent, yellowish or grayish white. 

 Butyrous: translucent and yellow. 

 Ceraceous: translucent and wax colored. 

 Opaque. 



Cretaceous: opaque and white, chalky; dull, without luster. 

 Dull: without luster. 

 Glistening: shining. 

 Fluorescent. 

 Iridescent. 



p\ pW h^ fW^ |Vio Fig. 37. Character of bor- 



\ \ |\ S S ders f colonies: * entire; 2 r 



' * I J ' * ' J ' -3 iinsliilafa- S ,.or>a.,rl A lrVol 



; 3, repand; 4, lobate- 

 lobulate; 5, auriculate; 6, lac- 

 erate; 7, fimbriate; 8, ciliate; 

 9, erose. 



In the study of colonies it. is necessary to observe their 

 general appearance, color, 1 and whether they are well iso- 

 lated or run together (confluent), observing the shape and 

 character of the edges. They should be examined with a low 

 power lens in order to determine any special markings which 

 may be characteristic. 



Estimating the number of colonies on plates. If the 

 number of colonies is not large (not exceeding 100), they 

 may be counted and the exact number recorded. When the 

 number is larger it is more convenient to divide the total 

 area into smaller areas and count the number of colonies in 



1 Saccardo, Chromotaxia sen Nomenclatur Colorum. This is a 

 very helpful color chart for descriptions. 



