To prevent discoloration and mildewing of the plants, the papers around them must be changed at the end of the following successive intervals: two days, three days, five days, one week, etc., until they are quite dry. The length of time required for pressing and drying depends upon the quantity of sap in the plants and also upon the dryness or humidity of the atmosphere.
Mounting.—When dry, the specimens are mounted on sheets of heavy white paper. These sheets are cut to a standard size, eleven inches by fourteen inches, or sheets of half this size, namely, seven inches by eleven inches; are permissible. The best method of attaching the plant to the sheet is by pasting narrow strips of gummed paper across the plant in such positions as will serve to hold all parts of it in position.
Labelling.—The name of the specimen, the date of collection, the place from which collected, and the name of the collector are to be neatly written in a column in the lower right-hand corner of the sheet. Printed labels which are pasted on this corner of the sheet are also used.
Collections of leaves may be prepared by the same process as that given for plants. Leaves will retain their autumn tints if their surface is covered with varnish or paraffin, which will prevent the admission of air.
To cover with paraffin dip the leaf for a moment into melted paraffin.