376 PHYTOGKAPHY. 



evenly distributed. Hence it is best to have these sections not 

 over five or six inches in thickness, nor should the pile itself 

 be carried too high, never exceeding two feet. Painted binders' 

 boards may be used, instead of the common boards, to separate 

 interior divisions. Some botanists use a kind of lattice made of 

 two Ia3*ers of thin strips or laths, crossing each other. This is 

 said to allow free escape of the moisture by evaporation, and so 

 to accelerate drj'ing, as in the case of the wire press. 



790. For 'giving pressure, various ways have been contrived. 

 The Screw-press is convenient and compact, but objectionable, 

 because it does not follow up the pressure as the plants shrink 

 in drying. This objection does not apply to the Lever-presses, but 

 they are usually unwiekty. Fortunately, one of the best forms 

 of the diying-press, as well as the simplest and cheapest, is 

 merely a board with weights placed on the top of the pile of 

 specimens. Here the pressure is continuous, constant!}' follow- 

 ing - the shrinkage of the plants. The weight on a pile should 

 vary from 25 to 100 pounds, according to the nature of the 

 specimens and the quantity in the press. On an average, 60 

 pounds is sufficient for most plants. If much greater pressure 

 is used, there is danger of crushing the more delicate parts of the 

 specimen, and thereb}' impairing its scientific value. For weights, 

 bars or masses of iron may be used, boxes filled with sand, 

 stones, and the like. 



791. Specimens brought home in the botanical box must be 

 placed in such thin specimen-sheets as are used in portfolio. 

 In putting plants in specimen-sheets, whether in portfolio or 

 press, it is well to take some pains to spread out the specimens 

 neatly ; for a little care now may save much later labor. How- 

 ever, with most species, any carelessness in this respect can 

 be remedied at the first change of driers. But there are some 

 plants, previously referred to, so peculiarly sensitive that what- 

 ever adjustment the}' receive must be given at the time they are 

 first placed in their sheets. 



792. Although plants can, if necessar} 7 , be kept fresh for several 

 da}'s in box or portfolio, on returning from a collecting trip they 

 should be transferred to the home press as early as possible. In 

 the transference, particular care should be taken to straighten 

 out and remove all folds and crumpling of the leaves, petals, 

 fronds, &c., and to arrange the specimen as naturally as possi- 

 ble, so as to show the proper habit. Both sides of the flowers 

 and leaves should be exhibited. Plants that were put directly 

 into press should receive this special attention at the first 

 change of driers, which on this account should be made within 



