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too miicli, since the specimens will eventually liave to be 

 examined externally and internally. If pressed too hardj the 

 surfaces may become altered beyond recognition, hollow organs 

 may be crushed, and overlying parts so cemented together that 

 the}' can only be torn asunder. Specimens well dried under 

 moderate pressure will be found to exhibit not only the external 

 characters well, but also, as a rule, to resume, when soaked, their 

 original shape, so that they can be studied in detail. Trouble, 

 however, may be caused owing to the unequal thickne-ss or con- 

 sistency of different parts of a specimen, as for instance where 

 thick stems are associated with thin leaves, or coarse, dry leaves 

 with delicate flowers. In those cases, extra padding with small 

 2)ieces of paper or of wadding must be introduced within the 

 '^retainer" iso as to distribute the pressure more evenly or more 

 in accord with the requirement of the several parts. These 

 paddings are, of course, of a permanent nature, and should not be 

 removed until the drying is completed. 



The requisite pressure may be applied by weights, or better, 

 b}' means of buckled straps, and it should be evenly distributed, 

 A sufficiently strong board should be placed on the top of each 

 2)ack of paper to carry the weights, or if strapping be adopted, 

 the packs should be placed between two such boards, or prefer- 

 ably trellis-like gratings (^^ presses '') made of wood or ware. 

 When straps are used to apply j^ressure, gratings are more useful 

 ihan solid boards, because they are lighter, and admit of evapora- 

 tion, and the straps, which may be of leather or strong webbing, 

 render the regulation of the pressure an easy matter. The 

 gratings may be made of strong wire or of w^ooden staves or laths 

 laid crosswise so as to leave openings of about 1-1| inch square. 

 Generally, wooden gratings will be sufficient, and they have the 

 double advantage that they are light, and can easily be made 

 wherever wood is at hand ; but Avhere the gratings are liable to 

 be exposed to very rough handling, they should be of strong 

 wire. A screw press should never be used."^ When moving about, 

 the collector should have his drying apparatus as simple as 

 possible, so that repairs and replacements of worn-out or lost 

 parts can easily be effected, 



^ Trellis or grating presses will answer well under almost any 



circumstances. They can easily be moved with their contents, 



suspended in the sun or over a fire, or be stood up on their narrow 



sides so as to expose the maximum surface to the air. On the 



other hand, drying under weights is only practicable when the 



collector is in residence, or able to stay at one place until the 

 drving is done. 



The nature, of the specimens.— Most plants lend themselves 



more or less readily to drying under pressure between absorbent 

 paper without any special prerautions. Not a few, boweTer, 

 require soine preparation before they can be pressed, while others 

 nre^ altogether unsuitable for that "process, either in part or in 



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