454 ACTIN0MYCETE8. 



fied, so that finally round, pea-sized, chalky crusts float 

 in shallow cups (67, v and vi). 



(6) Magnified sixty times : Very young colonies consist 

 of a confused ball of threads; older ones appear but 

 slightly transparent, with zones having wavy, jagged boun- 

 daries, all of which are darker in their peripheral por- 

 tions. The edge of the colony is beset with delicate 

 threads, like a fringe, which extend outward into the dis- 

 colored gelatin (67, vn). 



Gelatin Stab. — The surface growth is like that on the 

 gelatin plate. Sometimes drops of fluid (no oil!) are seen 

 upon the surface of the growth. The gelatin is very slowly 

 liquefied from above downward. In the stab the short, 

 radiating tufts of fibrils, which even at first develop, can 

 be observed for a long time (67, i). 



Agar Plate. — (a) Natural size: As upon gelatin. 



(6) Magnified sixty times: After about six days no struc- 

 ture is distinguishable in the dense colonies; they are 

 dark and homogeneous and surrounded by distinct fringes 

 (67, vm). 



Agar Stab. — Upon the surface the growth at first is 

 rather moist, with a yellowish luster and elevated like the 

 head of a nail; later it is drier, tough, and somewhat 

 puffed. The agar is discolored brown. In the stab there 

 are radiating, bristle-shaped branches (67, in and iv). 



Agar Streak. — The growth spreads out only moder- 

 ately, presents (after four to six days) a brownish color, 

 and on the thinner parts of the agar a white, chalky, 

 peripheral zone. In the course of time the whole becomes 

 whitish and chalky. Upon the clear water of condensation 

 there later forms a tough, brownish film, which also de- 

 velops chalky, white air hyphse, especially on the glass 

 walls (67, ii ). At other times a clumpy growth is pres- 

 ent at the bottom of the water of condensation without any 

 pellicle. 



Bouillon Culture. — At first a delicate and later a dense 

 pellicle. In grape-sugar bouillon there are thick, clumpy, 

 radially arranged masses on the bottom. The bouillon 

 becomes brown. 



Milk Culture. — Dense, yellowish-brown to cinnamon- 

 colored layer on top. The milk is clarified and alkaline. 



