620 PRESERVATION OF MOIST SPECIMENS. 



outside boards, and these ought to be thicker and stronger than the rest ; others 

 are inside boards, about f of an inch thick. For every two reams of drying 

 paper, not less than ten boards shall be procured ; two of which are for the 

 outside, and eight for the inside. Sheets of stout pasteboard are also useful 

 for packing up the plants as they become dry. The pressure is best applied 

 on a botanical excursion by means of a rope put twice round the boards and 

 paper, and tightened by a rack-pin. This is much better than straps, which 

 are apt to give way, and are with difficulty replaced during an excursion. 

 In other circumstances, pressure is best applied by means of heavy weights. 

 The pressure ought not to be less than 100 Ibs. This is preferable to a 

 screw-press, in which the pressure is not kept up while the plants are losing 

 their moisture. In the case of plants with strong stems, they must either 

 be split, or a sand-bag, of the same size as the boards, used, so as to equalize 

 the pressure. 



1206. Process of Drying. The plants when collected are to be placed on 

 the drying paper. In doing this, a parcel of not less than four sheets is put on 

 one of the outside boards ; then the specimens are laid out carefully, preserving 

 as far as possible their natural habits, and laying out the leaves and other parts. 

 Another parcel of drying paper is then placed above these, and the same pro- 

 cess is repeated with other specimens until twelve such parcels have been placed 

 together. Then one of the inner boards is laid down, and other layers of paper 

 and specimens are applied, until the whole parcel is of sufficient size to be sub- 

 jected to pressure. After twelve hours pressure, in most instances, the paper 

 is changed, the moist paper being hung up to dry ; and in transferring the spe- 

 cimens from the wet to the dry paper, a large pair of surgeon's forceps is used. 

 The interval elapsing between the changing of the paper may be increased or 

 diminished according to the nature of the plants, and the state of the weather. 

 In the course of eight or ten days, ordinary specimens will be so dry as to 

 require only very slight pressure, with a moderate circulation of air. Some very 

 dry plants, as grasses, may require only one changing. Some very succulent 

 plants require a long period of pressure, and constant changing ; and many of 

 them, such as Stone-crops, must be killed by immersion in boiling water for 

 five or ten minutes. Orchideous plants should be put into warm paper, and 

 changed frequently, with the view, if possible, of preserving their colours by the 

 rapidity of drying. Scarification has sometimes been adopted with the view of 

 allowing the juice to flow out rapidly. At the time the specimens are laid out 

 on the drying paper, a label should be inserted with the date of collecting, the 

 name of the station, its elevation above the sea (if it can be ascertained), and 

 any remarks as to soil or geological structure that may be known. With the 

 view of transporting dried plants securely in wet weather, it is useful to have a 

 supply of oil-cloth to cover them. 



1207. Mosses may be collected in excursions in tufts, and dried by moderate 

 pressure at first. They can afterwards be separated, moistened and dried with 

 greater pressure. They ought to be gathered in fructification. Lichens some- 

 times require to be taken with the rocks or stones to which they are attached, 

 and they may be merely wrapped up in paper. Sea-weeds must be washed with 

 fresh water before being laid out. The more delicate kinds are floated out on 

 pieces of stiff paper, and afterwards dried by moderate pressure. In preserving 

 fungi, such as Agarics, &c., a thin slice is taken from the centre, extending from 

 the top of the pileus to the base of the stipe. This is dried separately to show 

 the gills or pores, &c. The inner cellular portion of the pileus and stipe is then 



