COLLECTING AND PRESERVING CHAROPHYTA. 95 



mination, since no reliable determination can be arrived 

 at without the aid of a microscope. For examination 

 of dried specimens reagents will often be found useful. 

 The Char as usually secrete a large amount of lime, which 

 has to be removed before the plant can be examined. 

 This is successfully ensured by placing the piece to be 

 examined in a weak solution of sulphuric, nitric, or 

 hydrochloric acid. The acid, moreover, has the effect 

 in many instances of reviving the tissues. For the 

 Nitellese, which do not secrete lime in the same way, 

 strong ammonia sometimes serves as an effective reagent. 

 The piece to be examined may be placed on a slide, a 

 little ammonia dropped on it, and then boiled over a 

 spirit-lamp. The specimen should be well washed before 

 mounting. Iodine is often found useful in preparing 

 specimens for examination. 



For histological study it will be found convenient to 

 keep growing plants. If not exposed to too much light 

 most of the Charophytes will grow well in tanks, bell- 

 glasses, or even comparatively small jars, with a small 

 amount of earth at the bottom. It is best to keep each 

 species in a separate receptacle, to use rain-water to 

 avoid incrustation, and to have a few of the common 

 fresh-water moUusca in each receptacle to prevent the 

 plants being choked and the glass discoloured by minute 

 Algae. 



G. E. B.-W. 



