BULLETIN 39, UNITED STATES NATIONAL MUSEUM. [36] 



The method of mounting with gummed strips, while it perhaps re- 

 quires more time and work, is in many respects a pleasanter one than 

 that with glue. In this case sheets of the same paper used for mount- 

 ing, or similar paper without lines, are gummed entire on one side with 

 mucilage. It is cheaper to make the mucilage from pure gum arable 

 by simply soaking it in the proper amount of tepid water. To this, 

 however, it is much better to add a small quantity of glycerine, which 

 prevents, to a great extent, the tendency of the gummed sheets to roll 

 up at the edges on drying. To gum the sheets, lay them on a flat board 

 or other surface and fasten each corner with a pin gently driven through 

 the paper into the board (which should be of soft wood). It will be 

 found a great saving of trouble to have the board just a little narrower 

 and shorter than the sheet to be gummed, so that the mucilage can be 

 applied to the edges without danger of sticking to the board. A brush 

 of any convenient size maybe used to lay on the mucilage. The latter 

 should not be too thick, otherwise the coating will be uneven, but at 

 least two coats will be required to give it the proper adhesive power. 

 The second coat is put on after the first has become dry. If several 

 sheets are gummed at one time, which is the best way in order to con- 

 sume all the mucilage made at once, they may, when dry, be kept in a 

 large book or under some pressure to prevent them from rolling up. 



To cut the strips shears are not to be recommended, although with 

 skill they may be used. The difficulty will be to cut them of a uniform 

 width. It is better to cut them with a sharp knife on a broad jjiece of 

 pasteboard to a straight-edge. For this latter a thin board, six or eight 

 inches wide and considerably longer than the sheet to be cut, is much 

 more manageable than a narrow rule. The under surface of this board 

 should be rough and the edge smooth. The point of the knife must be 

 kept sharp, and it should have a thin blade. An ordinary shoe-knife is 

 better than a jackknife or penknife. An ink-eraser is a tolerable sub- 

 stitute. The average width of the strips should not be over 1^ lines, 

 but occasionally a wider one will be needed for thick stems. One sheet 

 may be cut up at a time and when consumed another cut. The long 

 strips thus cut may then be, most of them, cut into short pieces of from 

 half an inch to two inches in length, the ordinary length required being 

 about three-fourths of an inch. A few long strips should be left uncut 

 for special cases as they arise. 



In mounting with gummed strips, the specimens may be deliberately 

 adjusted to the sheets and then fastened down. A wet sponge is needed 

 to moisten the strips which are placed over the stems, peduncles, peti- 

 oles, etc., wherever they are required to make the plants secure. They 

 should generally be placed over the tips of pointed leaves, and may lie 

 over some flowers without concealing their essential parts. In putting 

 them down, care should be taken to brin^ the whole of the gummed 

 surface into contact with the paper, except only as much as is occupied 

 by the plant, which needs to be tightly encompassed and snugly held 



