APPENDIX A. 



THE following list of reagents is not intended to be an 

 exhaustive catalogue of the various substances in use in the 

 Botanical Laboratory : it includes, however, those reagents 

 which are considered to be of the greatest importance, in 

 elementary teaching, together with notes on their proper pre- 

 paration, and uses. 



Acetate of Potash. A strong solution in water is used as a 

 mounting medium for preparations of green parts of plants : 

 in this solution they retain their green colour for a long time. 

 Aluminium acetate may also be used for the same purpose. 



Acetic Acid. This is usually used as a dilute solution in 

 water (i per cent.) : it dissolves calcium carbonate with evolu- 

 tion of bubbles of CO 2 : it brings out the nuclei very clearly, 

 and with this object in view it is used with methyl-green : it 

 may also be employed as a corrective after treatment of a pre- 

 paration with potash, if the tissues have become too transparent. 

 Glacial acetic acid is also sometimes used in the preparation of 

 the apex of Fucus. 



Alcohol is of universal use as a solvent, precipitant, and 

 hardening agent. Absolute alcohol is the best, but for most 

 ordinary work strong methylated spirit will do. It dissolves 

 chlorophyll and other colouring- matters, resins, ethereal oils, 

 and some fixed oils : wax is soluble in hot alcohol. It precipitates 

 some substances, such as sugars, inulin, and asparagin. It 

 coagulates proteids, and has a peculiar action on some crystal- 

 loids. It acts as a hardening agent on cell-walls, sometimes 

 rendering them too brittle : this may be overcome by soaking 



