APPENDIX II 473 



mitosis, germination, maturation, fertilisation — a study of 

 the chromosomes requires a series of slides made at the 

 right time and position in one or more directions. 



For this purpose a microscope should be employed. So 

 many works dealing with the microscope have been published 

 that it is unnecessary here to give any but general hints on 

 this head, and reference may be made to Cross and Cole's 

 ' Modern Microscopy,' whilst useful hints will be found in 

 Cavers's 'Practical Botany,' Bower's 'Practical Introduction 

 to Botany,' Stevens' 'Plant Anatomy,' Zimmerman's 'Bo- 

 tanical Microtechnique,' Lee's 'Microtomist's Vade-mecum.^ 



The microscope should be a compound microscope, 

 preferably a Zeiss, with a rigid, firm stand, with suitable 

 eye-pieces, and a set of objectives of high and low power. 

 The tube should be neither too long nor too short. There 

 should be a coarse and a fine adjustment. There should be 

 a nose-piece fitted above the objective to carry a high and 

 low power. The stage on which the object is placed should 

 be provided with clips for the slide. Below the stage is the 

 diaphragm (preferably an iris) for control of the illumination 

 supplied by light falling on the mirror, a small hole being 

 used with a high power {e.g. \\n.) and a large hole with a 

 low-power {e.g. i in.) objective. The latter magnifies 60-80 

 diameters, the former 300-400 diameters. Keep the micro- 

 scope in good order, the parts oiled where necessary, and 

 the eye-piece, lens, and mirror clean. Examine objects in 

 light from a north aspect — /. e. not too direct. The micro- 

 scope should be vertical when the object is in position, and 

 a low power should be used first, then a high power, in the 

 last case taking care that a cover-glass lies over the object. 

 With a low power the flat mirror should be used ; with a 

 high power the concave mirror. Focus with the coarse 

 adjustment first, then, especially with the high-power object- 

 ives, with the fine adjustment. The slide must not touch 



