240 COOKE, ON MICROSCOPIC FUNGI. 
be written, and attaching several of these species-papers to a larger 
or genus-paper, or by devoting each larger paper to a species, adding 
in future other varieties, and enclosing all the species-papers of the 
same genus within a folded sheet, on which the name of the genus is 
written. 
“We have adopted, for our own herbarium, the ‘foolscap’ size. A 
sheet of paper receives within its fold the specimens of a single 
species; these are affixed to the right-hand page, when the sheet is 
open, and a small envelope is attached by its face to the same page 
at the bottom, in which loose specimens are kept for minute and 
special examination, or as duplicates. When the sheet is folded, the 
specific name is written at the right-hand lower corner, or, what is 
better, a strip containing that name and its number is cut from a 
copy of the ‘ Index Fungorum,’ kept for the purpose, and gummed 
in its place. The remainder of this page, which is of white cartridge 
paper, is occupied with memoranda referring to the species enclosed, 
sketches of the spores, synonyms, references to descriptions, &c. Ali 
the species-papers of each genus are placed together within a sheet 
of brown paper, half an inch larger in each direction, with the name 
of the genus written at the left-hand corner. <A piece of millboard, 
the size of the covers, when folded, separates each order. 
“When a leaf, or other portion of a plant, is to be examined under 
the microscope, with the view of determining the genus and species 
of its parasite, it may be fastened with small pins to a piece of sheet 
cork, two or three inches square, and about one eighth of an inch in 
thickness, such as used for lining entomological cabinets, and so 
placed under a lens that it may easily be brought into focus, and both 
hands left at liberty; or a dissecting microscope may be used for the 
purpose. From one of the pustules the spores may be removed on 
the sharp point of a penknife, and placed in a drop of water on a glass 
shde. A thin glass cover is placed over the drop of water, and the 
slide is submitted to examination. For further satisfaction it will 
often be found necessary to make carefully a thin section of a pustule, 
and place this under the microscope, a more troublesome but also 
much more satisfactory method. Reference to the Appendix will 
soon determine the name and position of the fungus, provided it 
belongs to the section to which this volume is devoted. 
“Tf it is thought desirable to mount the spores as permanent 
objects, there is no obstacle to such a proceeding. The spores of the 
different species of Aregma, of Triphragmium, and many of the Puc- 
cinie, will be worth the trouble. We have tried several media, and 
only adopted glycerine or balsam; either of these, especially the 
former, if the greater difficulty of securely closing can be overcome, 
will answer the purpose.” 
Nor let any one suppose that the work of explaining these 
minute organisms is one of mere amusement alone. In the 
very names of rust, smut, mildew, and mould, we have sug- 
gested to us the destruction of our forests and the loss of our 
crops; and the student of these forms will find that it is only 
by an intimate knowledge of the nature of the fungi which pro- 
duce these destructive diseases of plants that man can expect 
to control or prevent their attacks. The study of the micro- 
scopic forms of fungi attacking plants has led to researches 
