Generic Characters in the Coccaceae 



163 



at the same time. We are somewhat surprised to lind that the vis- 

 ible differences between the cuhures were due almost wholly to two 

 properties — chromogenesis and the general vigor of surface growth. 

 There was a distinction in luster between a large majority of the 



1 



2 



I 



n Ri IV 



VI VD Yin IX 



4 



5 

 6 

 7 

 8 

 9 



Fig. 3. — Distribution of 500 cocci according to chromogenesis. Roman numerals, hues; Arabic 

 numerals, chromos. 



cultures w^hich had smooth and shining surfaces, and a few which 

 were dull and rough. This difference appears, however, to be due 

 simply to the relative amount of growth and moisture in the tube. 

 Faint growths are moist and shining, while heavy growths in tubes 

 which do not contain much moisture show the dry, rough, dull 

 appearance. The "white chromogens" showed another slight 

 difference, varying from an opaque porcelain white to a duller and 



