MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 15 



it has passed all around the plug and become a chocolate brown. Later it becomes dry looking, 

 but is still glistening, and never becomes wrinkled. 



Bouillon. — Becomes diffusely cloudy by the third day, and liocculi form on the surface. After 

 two weeks the bouillou becomes a pale green, and a whitish deposit forms at the bottom. 



Bosolic acid. — Color becomes darker in four to six days. 



Litmus milk. — Becomes more blue by the third day and is a pure blue by the fifth day. 

 Later, a whitish deposit forms at the bottom. There is appearantly no change in the milk itself. 

 Reaction alkaline. 



Sugar gelatin, deep stab. — Growth confined mainly to the surface as iu plain gelatin. After 

 some time the surface growth become concave, though no softening can be detected. There is 

 no formation of gas. 



Indol. — Faint reaction on addition of both sulphuric acid and sodium nitrite. 



Relation to temperature. — Grows better at room temperature than at 35° to 36° C. 



Cladothrix Dichotoma (Cohn). 



(Fig. 10, PI. I.) 

 Synonym: Hrown Cladothrix (Bolton). 



Found often in the upper layers of made and virgin soil. Widely distributed. It is also often 

 found in the water of the Schuylkill and other rivers. 



Character. — No growth iu an atmosphere of hydrogen. 



Morphology. — Forms long chains and filaments, with the characteristic false branching which 

 distinguishes the genus. The rods are of very variable length, many of them being club-shaped. 

 Spiral forms are also observed. 



Spores have not been demonstrated. 



Motility. — Non-motile. 



Flagella not demonstrated. 



Colonies on gelatin plates. — Colonies appear on the second day as minute white dots, x 80. 

 They are seen to be made up of a tangle of fine lines, the center being so dense that no structure 

 can be positively made out. Toward the edge the lines are wavy and project some distance into the 

 gelatin. At the end of forty-eight hours the deep colonies are one sixth of a milimeter in diameter, 

 while those on the surface are one-half of a milimeter. Both have acquired a brown color, which 

 extends some distance into the surrounding gelatin, x SO. The deep and surface colonies look 

 much alike, the general structure being the same. The deep colonies grow gradually less dense 

 from the center to the edge, while on the surface there is a tolerably well-defined line of division 

 between the dense central portion and the surrounding corona, marking no doubt the outline of the 

 original growth as it broke through to the surface. Each colony lies in a saucer-shaped depression, 

 and after three to four days a thick brown skin has formed on the liquefied gelatin. At the end of 

 five days the largest colonies are about 3 mm. in diameter, and the brown discoloration extends 

 about 3 mm. into the gelatin, the center being lighter than the surrounding gelatin, x 80. The 

 center is two dense for the structure to be made out, and is brownish in color. The corona is 

 made up of fine wavy lines piercing the gelatin, but they are much shorter in proportion than in 

 the younger colonies. 



Agar slant. — At the end of twenty-four hours a whitish line has formed along the inoculation, 

 and the agar has already become a brown tint for 2 or 3 mm. on each side of the growth. The 

 band soon becomes wider and bends across its long axis, sometimes being thrown into wrinkles. 

 It takes firm hold on the agar, and has a dense gristly feel to the needle. It is hard to take 

 np any portion of the growth or to spread it on a cover glass. It has to be broken up by long 

 rubbing and even then many dense masses are left. The agar becomes a beautiful clear brown 

 throughout. 



Gelatin stab. — Very slight growth occurs down the line of puncture, and a button forms on 

 the surface, which has begun to sink by the end of twenty-four hours. The gelatin becomes a 

 clear brown. At the end of a week the saucer of liquefaction is about (i mm. deep, and from the 



