228 



METHODS OF CULTIVATION 



This leveling is an important matter since the de- 

 velopment of a colony is to some extent proportionate 

 to the supply of medium available for its nutrition.. 

 Thus in a "smear" on sloped tube culture, the colonies 

 at the upper part of the medium are stunted and small 



FIG. 122. Plate-levelling stand. 



but increase in size and luxuriance of growth the 

 nearer they approach to the bottom of the tube, 

 where there is the greatest depth of medium. 



3. Place three sterile Petri dishes in a row on the 

 surface of the glass plate and number them i, 2, and 

 3, from left to right. 



FIG. 123. Plate-levelling stand, side view. 



4. Number the previously liquefied tubes of nutrient 

 media i, 2, and 3. Flame the plugs and see that each 

 plug can be readily removed from the mouth of its 

 tube. 



5. Add one loopful of the inoculum to tube No. i, 



