SPECIMENS TO BE CLEANED BEFOBE MOUNTING. 39 



it with fresh specimens, its peculiar character will be 

 observed. 



In mounting with Canada balsam, the great art ap- 

 pears to consist in laying on the balsam at the right 

 moment, that is, when the plant and edges are not too 

 moist ; for, when this happens, a sort of dew will be 

 formed on the balsam : and, on the other hand, if too 

 dry, the cells and fine ramuli of the specimen will have 

 become considerably shrunk. 



It need scarcely be remarked that, in whatever way 

 the mounting may be performed, the specimens should 

 be previously cleaned of parasites, whether other spe- 

 cies of Algee, Diatomacese, or zoophytes. Though it 

 has been before stated that Canada balsam is not suited 

 for the Chlorospermeae, yet for some of the larger and 

 coarser weeds it answers exceedingly well, and shows 

 the cells very distinctly. 



If it is required to mount specimens of plants already 

 dried, in Canada balsam, they must be immersed for a 

 few minutes in sea-water, then rinsed in fresh water, 

 and afterwards treated in the same manner as recent 

 specimens. 



