[Vol. 9 



<%2 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



of meat extract, dehydrated Bacto beef, and Liebig's meat ex- 

 tract. The dehydrated beef gave better growth but required 

 much longer time to make and resulted in a turbid, dirty product, 

 making hydrogen-ion determinations by indicators very difficult. 



Agar Plates. — On peptone-beef agar poured plates, P H 6.6, kept 

 at 20° to 25° C, colonies appeared within 48 hours. They were 

 white, round, smooth, and in 4 days well-separated surface colon- 

 ies measured as much as 6 mm. in diameter. At first they showed 

 a bluish tinge but later they became opaque white with a some- 

 what faintly colored creamy yellowish center. The margin was 

 entire, with a conspicuous colorless zone 2 to 4 mm. wide sur- 

 rounded by a marked whitish discoloration of the medium which 

 was most conspicuous at the border of the colorless zone and 

 gradually faded out into the color of the surrounding medium. 

 The whitish discoloration might be recognized at a distance of 0.5 

 cm. from the colorless zone at the end of the fourth day although 

 it was faint at this distance. The colony was somewhat sticky 

 to the touch of a needle but was not viscid; it was glistening, 

 somewhat raised or convex, and internally appeared amorphous, 

 that is, without distinctive markings. As the medium dried out 

 the colonies became indistinct and gradually disappeared from 

 view. Buried colonies made but little growth. On Ph 7.2 pep- 

 tone-! >cef agar growth was the same but there was no colorless 

 zone or precipitate. 



Agar stroke. — At 25 to 30° C. there was a moderate amount of 

 growth in 48 hours, often reaching a width of around 4 mm. at the 

 base of the slant and tapering upwards. The growth was filiform, 

 raised, glistening, smooth, and opaque white to creamy white, 

 odor was absent or not marked, and the consistency was that of 

 melted butter. Growth was very marked at the base of the slant 

 and in the water of condensation and of syneresis. As the smears 

 became old there was a tendency to form a slight, thin growth at 

 the margin which upon close examination appeared in the form 

 of irregular, fine, thread-like projections. Below Ph 7, a colorless 

 region surrounded the smear and this region in turn was bordered 

 by a dense white precipitate. This precipitate became very 

 marked by the third or fourth day. Above P H 7 there was no 

 colorless zone or precipitate. 



Agar stab. — There was good growth at the surface and slight 

 growth in the upper part of the stab. There was no growth in 

 the lower part of the stab. 



