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 ot 

 many objects, a simple stage-microscope is indispensable. It 

 should be furnished with only the best lenses, preferablj- 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 raa^' 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 objec^t to be ex- 

 amined, an adjustable tube carrying two combinations of lenses, 

 the objective and the eye-piece, and flnallj- 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 simplicit}' 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. 



