OF THE CHARACE.E. 113 



repeated until a convenient pile is formed, which should be 

 forthwith submitted to the press. After the lapse of a few 

 hours the damp blotting paper must be removed, and 

 replaced by dry material, special care being taken not to 

 disturb the stearine covering, as the Characeaa are very apt 

 to cling to it : but this is of no consequence, as they will 

 easily separate as soon as the specimen is perfectly dry. 

 If, on finally removing them from the press, the plants do 

 not adhere completely to the paper on which they lie, a 

 little gum-arabic may be placed under the stem and prin- 

 cipal branches. 



The extreme fragility of the Characege must never be 

 lost sight of during their preparation, and the drier they 

 become, the more strongly marked is this tendency to break 

 up into fragments. This tendency remains even after they 

 are placed in the herbarium : the only remedy I can sug- 

 gest is to insert a very thin layer of common wadding be- 

 tween every half-dozen sheets of the prepared specimens. 

 The wadding, however, must be previously moistened with 

 benzine or corrosive sublimate, or sprinkled with camphor ; 

 otherwise it is but inviting the attacks of Anobia and 

 Dermestes, and similar destructive insects. 



The Characeaa being of a comparatively large size, a low 

 power only of the microscope is needed for determining 

 their characteristics ; indeed an ordinary lens is generally 

 sufficient. The stratum of carbonate of lime, which 

 invests the majority of these plants, must of course be got 

 rid of by means of an acid, before any observations can be 

 made on their inner structure. 



The species of Nitella, as being entirely free from this 

 incrustation of lime, afford the best opportunity to the 

 student of watching the wonderful phenomenon known, 

 in technical language, as ' cyclosis,' or ' rotation of the 

 protoplasm,' but commonly called l circulation of the sap : ' 

 tJiiSj however, it is not. Under a power of not less than 

 200, green globules are seen to circle round and round 

 each of the cells. But these globules are not the sap, 



