PKACTICAL BOTANY. 



i. 



METHODS AND REAGENTS. 



A. Making Preparations. 



Preservation of Material. In many cases it is 

 possible, and even preferable, to use fresh material, but 

 it is often convenient to keep it for a time ; the best 

 liquid for this purpose is ordinary methylated alcohol, 

 in such quantity as to completely cover the material. 

 It must be remembered that this will extract the green 

 colouring matter (chlorophyll) from the material im- 

 mersed in it, as well as resin and other substances. 



Hardening. It is not necessary, for the general 

 study of the histology of plants, to harden them, for 

 the tissues are usually sufficiently firm to admit of their 

 being cut satisfactorily. In the case of exclusively 

 parenchymatous tissues, especially those of cellular 

 plants, it is necessary to harden them somewhat, and 

 for this purpose dilute alcohol (50 per cent.) may be 

 used. 



B 



