OF THE CHARACEA2. 
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 Characeee 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 Characeaa 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 Characeas 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 1 rotation of the 
protoplasm,’ but commonly called ‘ circulation of the sap : 1 
this , 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, 
I 
