20 PRACTICAL BOTANY 



good penetration. Meanwhile the forefinger and thumb 

 of the left hand will be at liberty to move the slide on 

 the stage so as to bring into the field of view different 

 parts of the preparation. 



Observers should accustom themselves to using both 

 eyes indifferently, and when one eye is being used for 

 observation, the other should be kept open: a little 

 practice will soon overcome any difficulty which may be 

 at first found in doing this. 



Care is necessary in removing the slide from the 

 stage, especially when the high power has been used : 

 in this case the tube should first be raised so as to 

 remove the objective from close proximity to the stage, 

 and the slide should then be slipped off the stage, not 

 lifted off. Want of attention to these points is apt to 

 result in smearing the objective with glycerine, or 

 other media. 



Drawing from the Microscope. Nothing com- 

 pels attention to details of an object so successfully as 

 drawing it ; while, as it is impossible to make a drawing 

 of an ill-prepared object, the intention to make a 

 drawing will have its effect upon the care devoted to 

 preparation and mounting. It should le a rule for 

 students to draw every object they observe, not merely for 

 the sake of the drawings as memoranda, but in order 

 to acquire a habit of close observation. 



For drawing, a hard pencil (H.H.H.) is recommended, 

 and it must be cut to a fine point : paper with a hard 

 smooth surface is to be used, or better, a thin drawing 

 card or Bristol board with a hard surface. A decisive 

 style of drawing should be adopted, in which every line 

 is clear, and conveys its own meaning. 



