188 THE MICROSCOPE 



allowed to soak for five minutes, when the sections are ready for 

 mounting in balsam. It must be noted that the times given 

 above are only approximations, and will not hold good for all 

 cases, since the time required for the action of the stain is 

 materially modified by the thickness of the section, and by its 

 physical structure, and very possibly also by its chemical con- 

 stitution. It will be found in practice, that, for the general run of 

 wood sections, very little variation from the times indicated will 

 be required. When an alteration in this direction is necessary, 

 it will be within very narrow limits, and to carry it out success- 

 fully will not tax either the ingenuity or the patience of the 

 experimenter very severely. Wood sections stained by this 

 method make beautiful preparations. Not only are certain 

 portions of the section dyed green and crimson respectively, but 

 other portions acquire various intermediate tints, so that certain 

 sections of much diversity and complexity of structure, when 

 stained by this method, rival in splendour some of the diatoms. 

 We will give a few examples of pretty botanical sections : — 



Coffee Berry. — The unroasted berry should be soaked for 

 some hours in cold water until sufficiently soft (seeds should not 

 be allowed to remain too long in water, especially in warm 

 weather, otherwise they will begin to germinate, in which case 

 their internal structure becomes entirely changed), then imbedded 

 in paraffin and cut in the microtome, the section being made in 

 the direction of the long axis of the berry. Only a few perfect 

 sections can be obtained from each berry, for at the hiliim the 

 seed-covering turns in and penetrates the substance of the berry 

 to such a depth, that before many sections have been made, the 

 reflected covering will be cut down upon ; when this has been 

 reached, a circular ribbon representing the covering will — unless 

 in exceptional cases — fall from the centre of the section and mar 

 its beauty. Sections of the berry may be mounted in glycerine, 

 or if stained rather strongly with carmine, mounted in Canada 

 balsam and benzole ; the same method of treatment applies to 

 all other hard berries or seeds. 



Chicory.— After the student has got his slide of coffee he will 

 do well to prepare a longitudinal section' of unroasted chicory-root 



