FLORA OF WASHINGTON AND VICINITY. 227 



a book. It is held in the two hands, with the right (open) edge elevated 

 at an angle of about 45° from the table, and while the two thumbs 

 rapidly separate the edges of the sheets from the upper towards the 

 lower ones the eye glances at each label attached to the lower right- 

 hand corner of each sheet until the plant sought is reached. This 

 would scarcely be worth mentioning were it not for the fact, as every 

 one will early find out, that by far the greater part of the references to 

 the herbarium will be in search of species belonging to large genera. 

 Very large genera should be divided and kept in several genus-covers, 

 and it is an excellent plan to write on the outside the names of all the 

 species in a genus cover. 



Upon the whole, then, it is doubtless best to mount the specimens 

 of the herbarium, but this should not be undertaken at first or until 

 considerable experience has rendered one skilled in selecting the 

 very best specimens both from a scientific and an artistic point of view. 

 A new beginner will never afterwards regret having waited at least three 

 years before mounting any of his plants. By this time he will have seen 

 many other herbariums and received the specimens of other older botan- 

 ists in exchange to compare with his own, and will then i)ossess some 

 valuable ideas on the whole subject. This, therefore, though prooably 

 the most complicated part of a botanist's work, is, when thus viewed, 

 the one upon which the least pains need be expended in describing the 

 process, since if the proper course is pursued from the beginning he will 

 be sure to have already picked up nearly all the needed information re- 

 specting it before he undertakes to apply it to his own collection. 



The two principal methods of mounting may, however, be briefly 

 described. These are, first, with glue, and, second, with gummed 

 strips. In the first case a glue-pot of rather large size, say to hold a 

 pint of glue, or larger, is required, and a soft flat brush, li to 2 inches 

 in width, with which to spread the glue. The latter should be i^ure and 

 white of the best quality. The glue is made veiy thin, so as to be in a 

 free liquid state, and kept over a burner (gas-stove) at a temperature 

 nearly boiling.* The plant is first placed on a rough paper with what 

 is to be the upper side downward, and the glue is rapidly and dexter- 

 ously spread thoroughly over every x^art of the side that is to go down. 

 It is then immediately turned over and laid with precision upon the 



* The use of fish-glue, which requires no heating, is recommended by some. Although 

 I have not tried it, and therefore do not know the objections which may exist to its 

 use, it is certain that if otherwise equally good this must be v very strong point in 

 its favor. 



