54 Botanical Microtechnique 



as lot 1, piece 1, slide 3, row 2, section 5. This designation on a 

 drawing or photograph makes it possible to locate the exact section 

 used. 



In some subjects the cell size or character of the cellular arrange- 

 ment makes it impossible to relocate a given cell by row and section. 

 A calibrated mechanical stage should be used to study such material. 

 If the stage revolves, decide upon a reference point on the circular 

 vernier, clamp the stage, and study the slide. Having found a cell 

 which will be sought again for further study, take readings on the 

 longitudinal and transverse verniers, and record in )our. notes and 

 on drawings. It should then be possible at any future time to put 

 the same slide on the microscope, set the verniers to the recorded 

 readings, and locate the particidar cell in the field of view. 



