LEPTOTHRIX EPIDERMIDI8. 459 



Relation to Oxygen. — Grows better with the admission 

 of oxygen. 



Requirements as to Temperature and Nutrient 

 Media. — Grows luxuriantly and rapidly at room and in- 

 cubator temperature upon all nutrient media. 



Gelatin Plate. — (a) Natural size: At first, minute 

 white points which liquefy the gelatin as soon as they 

 become a little larger — after twenty-four to forty-eight 

 hours. The older colonies exhibit a small white flake in 

 the center of the liquefied areas; also the edges of the areas 

 present a whitish border (69, viii). 



(6) Magnified fifty times: Young, superficial colonies 

 present a pretty convolution of curly, wavy threads. The 

 center soon becomes dark and cloudy and sinks in, while 

 there remains a row of fine radiating hairs as a peripheral 



Fig. 24. — Leptothrix epidermidis Biz. 



zone. As the liquefaction advances there is finally a flat, 

 gray saucer, which presents a delicate hairy border toward 

 the solid gelatin, and in the center of which is a curly 

 mass whose structure becomes more and more indistinctly 

 crumbly (69, ix). 



Gelatin Stab. — After twenty-four hours there is formed 

 a conical area of liquefaction with whitish flocculi, and at 

 the apex crumbly, yellowish-white masses of bacteria 

 gradually accumulate. After four or five days there forms 

 a grayish, tough pellicle on the surface (69, i). 



Agar Plate. — (a) Natural size. Superficial colonies: 

 White or yellowish white, sharply outlined growths with 

 smooth but irregularly notched borders. The deep colonies 

 remain small, dense, yellowish-white (69, v). 



