Having found a plant infected with some rust or brand, and by means of a pocket lens assured yourself that it is such, although the power is insufficient to tell what it is, collect as many leaves as you are likely to require; place them flat one upon the other, to prevent their curling up at the edges, should the weather be hot, and yourself far from home, and lay them in your box; or if you should take in preference an old book with stiff covers, place them separately between the leaves of your book, and they will be in still better condition, if you desire to preserve them. Arrived at home with the results of your trip, proceed at once to lay them between folds of blotting-paper, submit them to a gentle pressure, and change the papers daily until your leaves are dry, not forgetting to keep a scrap of paper with each collection, stating date and locality, to which, after microscopical examination, the name may be added. When thoroughly dry, your leaves may be preserved for reference in old envelopes, with the particulars endorsed on the outside. Fungi on leaves will generally be examined to the greatest advantage in the fresh state, but if too much pressure is not employed in the drying, it will not be difficult even in that condition to make out their characteristic features. Care must be taken, by changing their position, that moulds of other kinds do not establish themselves upon the specimens in drying, or that when dried they do not fall a prey to _Eurotium herbariorum_. If it is intended to add these leaves to your herbarium, or to form a special herbarium for them, they should be mounted on white paper, first by affixing one or two leaves by means of thin glue to a paper about four inches square, on which the name, date, and locality may 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.