PREPARATION AND TREATMENT OF SPECIMENS. 277 



fingers. In most cases, however, it is advisable to squeeze them 

 between cork or elder-pith, or, if the substance is of a suitable 

 nature, it may be left to solidify in liquid gum. Thin roots, 

 single leaves, the tips of stems, and similar objects with sappy 

 tissue, may be cut between elder-pith, which is generally pre- 

 ferable to cork; the pressure must, of course, be regulated not 

 to injure the object. Thicker objects may require a suitable 

 groove to be cut in the pith. Longitudinal sections through 

 delicate thread-shaped objects are generally most successful if the 

 objects are bent round the edge of a flat piece of cork, one end 

 being firmly pressed down and the other (which may be fixed on 

 with a very little gum) carefully cut through commencing at the 

 edge. We have thus obtained thin median sections through the 

 soft ends of roots, after numerous unsuccessful attempts between 

 cork and elder-pith. The process of placing the preparation in 

 gum can only be employed with those objects which can be dried 

 without injury, and which re-assume their original shape on being 

 moistened ; with these, however, it is preferable to every other 

 process. Pollen-grains with thick extine, starch-grains, the outer 

 walls of epidermal cells, the thallus of lichens, the tissues of many 

 mosses and algre, &c., may thus be cut into the finest lamellae 

 without difficulty. 



For decayed wood and similar tissues with loosely united parts, 

 injection with melted stearine, which is afterwards removed on 

 the slide with ether or benzine, is said to be serviceable under 

 certain circumstances. Schacht states that he has obtained 

 delicate sections of very decayed wood from grave-mounds by 

 this treatment. 



Finally, objects which consist of only a single row of cells lor 

 layer of cells for, instance, filaments of alga? and leaves of moss 

 are usually placed upon the thumb-nail with a drop of water, 

 and cut by a swinging motion of the razor a process which may 

 also be employed for several positions of the cells with moderately 

 thick objects. 



In order to convey to the slide the sections lying in the liquid 

 on the blade of the knife or the thumb-nail, many observers 

 employ a fine brush, to the moist point of which the single objects 

 readily cling, whence they can just as readily be liberated again 

 in water. The razor may also be laid flat upon the glass plate, 

 the edge just touching the liquid ; the separate sections may then. 



