/. Introduction 



The study of the microscopic details of the structure of plants 

 usually requires some preparation of the material to facilitate obser- 

 vation. Unicellular, filamentous, or other minute plants require 

 comparatively little preparation. The material may simply be mounted 

 on a slide in a drop of water and thus studied, even under consider- 

 able magnification. Larger plants, or parts of plants, must ix- dissected 

 or cut into thin slices in order to expose inner regions and to permit 

 light to penetrate through the object. Some materials have enough 

 natural coloration to be visible even when finely divided or sectioned. 

 Highly transparent or colorless structures, on the other hand, must 

 be made visible by the use of stains. Preparations that are to receive 

 considerable handling over a period of time should have some 

 degree of permanence. The desirable properties of microscopic jMepa- 

 rations are, therefore, adequate thinness, coloration or retractile 

 visibilit), and permanence. 



The processes used in the preparation of plant materials for 

 microscopic study can be roughly classified in the following categories: 



1. Unicellular, filamentous, and thin thalloid forms can be pro- 

 cessed //( toto — without sectioning — and mounted as "whole mounts" 

 to make temporary or permanent slides. 



2. Some succulent tissues can be crushed or smeared into a thin 

 layer on a slide or cover glass. The preparation is then stained and 

 treated to make temporary or permanent slides. 



3. The more complex and massive tissues are usually sliced into 

 very thin slices, freehand or with a microtome. Materials that are not 

 sufficiently rigid to be cut without support are embedded in a sup- 

 porting matrix before sectioning. The sections are stained and 

 mounted to make temporary or permanent slides. 



The method used for the perparation of a given subject depends 

 on the character of the material, the use that is to be made of the 



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