POTATO MEDIA 



165 



plate culture work. For "potato plates" slices from pota- 

 toes are cut as large and as thick as the relative sizes of 

 potato and dish permit (Fig. 114). The slices should be thin 

 enough not to touch the lid and thick enough to be firm. 



Fig. 113. — Petri dish with the lid partly raised. X 



Fig. 114. — A potato plate. X §. 



It is a good plan to wrap each dish separately in paper to 

 retain the lid securely, then sterilize as for potato tubes, 

 and leave plates wrapped until wanted. 



It sometimes happens that the natural acidity of potatoes 



