4 BULLETIN 109, IT. S. DEPARTMENT OF AGRICULTURE. 



MOLDS IN TRAGACANTH GUM. 



Tragacanth gum is usually bought in considerable quantities for use 

 in the larger factories, and, if the samples obtained in this investiga- 

 tion from several such sources were representative, the highest grades 

 of the gum are not used. It was thought possible that these gums 

 themselves might be carriers of molds, and several samples were set 

 away in sterile Petri dishes to which a small quantity of sterile dis- 

 tilled water was added. These cultures, like others to be described, 

 when not under observation were kept in a dark chamber in which 

 the temperature varied between 21.5° and 25° C. In three days all 

 the samples showed an abundant growth of molds, which began to 

 develop fruiting stages on the fourth day. For further study, cul- 

 tures were transferred to a medium containing one-half of 1 per cent 

 sodium chlorid, 1 per cent peptone, 1 per cent beef broth, and -j-iO 

 points acidity. Other cultures were also prepared on sterilized 

 tragacanth gum, partly prepared on a thick paste and partly on a 

 thinner paste. 



Cultures on beef agar and peptone flourished and yielded a variety 

 of organisms, which were turned over for identification to Mrs. Flora 

 W. Patterson, Mycologist of the Bureau of Plant Industry. Four 

 forms appeared with great regularity. Most conspicuous and quick- 

 est in growth were (1) RMzoporus nigricans Ehren., a large organ- 

 ism forming large, loose, conspicuous hyphal masses; (2) Mucor 

 racemosus Fres. var. brunneus Morini, a smaller organism rapidly 

 forming a loose, white mass of hyphse; and (3) Penicillium sp., a 

 somewhat slower organism in point of development, marked by its 

 white round-headed conidiophores. This organism in the early 

 stages was striking by reason of its brilliant whiteness, but as the 

 cultures grew older the more usual bluish color appeared. The last 

 common form was (4) Aspergillus candidus Link, a very small mold, 

 characterized by its slower growth, its dingy white color, and its 

 appearance in mixed cultures as a minute undergrowth among the 

 above-mentioned larger organisms. No attempt was made to carry 

 out a further study of these organisms. It seemed clear, however, 

 that the Aspergillus was more at home on the tragacanth medium 

 than on the beef agar and peptone as here offered. 



MOLDS ON WRAPPER LEAF. 



As it seemed very probable that the wrapper leaves, like most 

 other free surfaces, might give lodgment to spores of molds and 

 thus become agents of infection, it was thought desirable to see what 

 molds could be cultivated from them. Accordingly, cultures in the 

 media previously described were prepared from the washings ob- 

 tained by rinsing the surfaces of wrapper leaves with sterile water. 

 Several organisms were obtained in small quantities, and Mrs. Pat- 



