9i ON FRESH WATER ALG.E. 



Almost all species of Algae which are firm and semi-cartilaginous, 

 or almost woody in consistency, are best preserved by simply dry- 

 ing them, and keeping them in the ordinary manner for small 

 plants. The fresh-water Algae which bear this treatment well 

 belong to the Phycochromophycece, such as the Nostocs, Scytonema, 

 &c, the true confervas not enduring such treatment at all. When 

 dried plants are to be studied, fragments of them should be soaked 

 for a few minutes in warm, or for a longer time in cold water. 



The only satisfactory way that Algae can be finally prepared for 

 the cabinet is by mounting them whole or in portions, according to 

 size, for the microscope. Of the best methods of doing this the 

 present is hardly the time to speak ; but a word as to the way of 

 cleaning them will not be out of place. Many of them, especially 

 the large filamentous ones, may be washed by holdiug them fast 

 upon an ordinary microscope slide, with a bent needle, or a pair of 

 forceps, and allowing water to flow or slop over them freely, whilst 

 they are rubbed with a stiffish camel's-hair pencil or brush. In 

 other cases, the best plan is to put a mass of the specimens in a 

 bottle half-full of water, and shake the whole violently, drawing off 

 the water from the plants in some way, and repeating the process 

 with fresh additions of water, until the plants are well scoured. 

 At first sight, this process would seem exceedingly rough, and 

 liable to spoil the specimens, but I have never seen bad results 

 from it, at least when practised with judgment. The water seems 

 so to envelope and protect the little plants, that they are not 

 injured. 



After all, in many instances it appears impossible to clean these 

 Algae without utterly mining and destroying them, so that he who 

 despises and rejects mounted specimens simply because they are 

 dirty and unsightly, will often reject that which, scientifically speak- 

 ing, is most valuable and attractive. 



In finally mounting these plants, the only proper way is to place 

 them in some preservative solution within a cell on a slide. After 

 trial of solution of acetate of alumina and various other preser- 

 vative fluids, I have settled upon a very weak solution of carbolic 

 acid, as the best possible liquid to mount these plants in. Acetate 

 of alumina would be very satisfactory were it not for the very great 

 tendency of the solution to deposit minute granules, and thus spoil 

 the specimens. As every one knows, the great difficulty in pre- 

 serving microscopic objects in the moist way is the perverse ten- 

 dency of the cells to leak, and consequently slowly to allow entrance 

 to the air and spoil the specimens. 



As I have frequently found to my great chagrin, the fact that 

 a slide has remained unchanged for six months, or even a year, is 

 no guarantee that it will remain so indefinitely. It becomes, 

 therefore, exceedingly important to find some way of putting up 

 microscopic objects that can be relied on for their preservation. 

 Where carbolated glycerine jelly or Canada balsam can be used, 



