102 
OF THE MARINE ALGiE. 
to lay such monstrous specimens between sheets of writing 
paper, or to put them away in the herbarium cabinet. The 
consequence is, that they are more or less exposed to the 
action of the air, which is almost sure after a while to 
impart to them a considerable amount of moisture. 
In examining this class of Algte it is necessary (if his 
investigations are to be of any value) that the student 
should make himself acquainted with their anatomical 
structure. In numerous cases this is by no means difficult, 
On account of their transparent nature, which allows of 
their whole inner structure and delicate cellular tissue 
Deing examined at leisure under the microscope. In those 
species, however, which are furnished with a thick leathery 
frond and stem, it is requisite to cut fine sections, otherwise 
their opacity effectually prevents any view of the form and 
arrangement of the cells. [With regard to this part of the 
subject I must refer the reader to works in which the 
methods of preparing objects for the microscope are de- 
scribed at length : as, for instance, ‘ Davies’ Preparation and 
Mounting of Microscopic Objects,’ where the whole matter 
is thoroughly discussed. — Ed.] I will only observe here, that 
the examples to be operated on had better be quite diy, 
because in their wet state they are very apt to get tom 
instead of being accurately cut, the cells coming apart and 
hanging together in disorder. The section must be placed 
in water or spirits of wine, and left for awhile to absorb the- 
fluid ; it is then fit for examination on a slide. 
The lime-producing Algse (by which I mean Corallina, 
Jania, Acetabularia, Liagora, Melobesia, and similar genera) 
must not be submitted to the knife until the incrustation 
has been entirely dissolved by means of an acid. 
It is often very difficult to detect the true structure of the 
cell walls in the strictly gelatinous Alga?, as also in many of 
the Enteromorpha and some other families. The best plan 
in such cases is to add a drop of a solution of chloride of 
zinc and iodine to the fluid in which the section is im- 
mersed on the slide. By this expedient a conspicuous blue 
