30 



CIRCULAR NO. 118, BUREAU OF PLANT INDUSTRY. 



in order to insure an even distribution of the flocculent cellulose. 

 Tubes of this character, inoculated upon the surface with the spores 

 or mycelium of some cellulose-dissolving fungus and kept from 20 



to 40 days in a moist 

 atmosphere at a tem- 

 perature of 30° C, 

 show a cleared zone 

 in the upper layers. 

 The hyphse of the 

 fungus usually pene- 

 trate the medium for 

 only a few millime- 

 ters of the culture 

 medium, as shown in 

 figure 1. 



A tube in this 

 condition may be 

 scratched with a file 

 or diamond glass 

 cutter near the bot- 

 tom at the point 

 where it must later 

 be broken; the lower 

 half of the tube is 

 dipped in a disin- 

 fecting solution, such 

 as 0.2 per cent mer- 

 curic chlorid, and 

 wiped dry with 

 sterile filter paper. 

 The bottom of the 

 tube is cracked en- 

 tirely around and re- 

 moved by means of 

 sterile forceps; the 

 cotton plug in the 

 mouth of the tube 

 is pushed down the 

 tube against the cul- 

 ture, and the entire 

 plug of agar is forced sufficiently beyond the broken rim so that by 

 means of a sterile knife several sterile sections may be cut and trans- 

 ferred immediately to the surface of a previously cooled layer of 

 cellulose agar in a Petri dish. The cytase will diffuse slowly from 



[Cir. 118.] 



Fig. 1. — Culture tubes showing the action of Penicillium 

 pinophilum when growing upon media containing 

 amorphous cellulose. At the left a sterile tube of 

 cellulose medium is shown for comparison. 



