PHYSIOLOGICAL BOTANY. 



INTRODUCTION. 



HISTOLOGICAL APPLIANCES. 



THE instruments and other appliances used in the exami- 

 nation of minute vegetable structure are, with the exception of 

 a few special ones to be considered later, the following : - 



1. Simple microscope. For the preliminary preparation of 

 man}- objects, a simple stage-microscope is indispensable. It 

 should be furnished with only the best lenses, preferably doub- 

 lets or triplets, magnifying from ten to at -least twenty diameters. 

 The glass portion of the stage should be not less than an inch 

 and a half in diameter ; supports at the sides of the stage, on 

 which the wrists may rest during dissections, are of considerable 

 use. If the compound microscope described below is provided 

 also with an inverting eye-piece and with an objective of long 

 focus, it can be made to serve for most dissections ; otherwise a 

 simple microscope should always be at hand. 



2. Compound microscope. When reduced to its simplest terms, 

 this consists of a stage, or flat support for the object to be ex- 

 amined, an adjustable tube carrying two combinations of lenses, 

 the objective and the eye-piece, and finally some means of illu- 

 minating the object. The desiderata to be borne in mind in the 

 selection of a compound microscope for use in Vegetable His- 

 tology, are : excellence in the optical parts, ease and steadiness 

 in their adjustment, and simplicity of construction. Other things 

 being equal, a microscope with a short tube and with a low 

 stand will be most convenient, on account of the large number 

 of cases in which reagents must be employed, their application 

 requiring a horizontal stage. 



