SPERMATOPHYTES— GYMNOSPERiVrS 335 



Pinus strohus needs no preliminary treatment except a few hours' 

 soaking in water; but harder pines and most of the other conifers 

 should be boiled in water for 24 hours — there is no harm in letting it 

 cool overnight — and transferred to equal parts 95 per cent alcohol 

 and glycerin. Even soft pine may remain in this mixture for at least 

 a week, and it is a good plan to keep in this mixture, as long as pos- 

 sible, all woody material which is to be sectioned. Cut by the hot 

 steam method. The Durham duplex blade cuts better in the Spencer 

 holder, as now made; but the "Gem" or "Star" blade, with the back 

 broken off, is still better. The "Gem Double Life Razor Blade," with- 

 out the back, can be obtained from The American Safety Razor 

 Corporation, Jay and Johnson Streets, Brooklyn, N.Y. There is no 

 extra charge for these blades. With the much thinner safety razor 

 blades, the holder is likely to hit the block. Unless you can cut the 

 transverse sections of mature wood of Pinus strohus (white pine) at 

 20 fx or thinner, there is something the matter in preparing the wood, 

 in the microtome, in the knife, the angle of the knife, the steam, or 

 the technician. Safranin and Delafield's haematoxylin is a good stain 

 for any mature wood. 



If you are in a hurry, soak the blocks in hot water 30 minutes, cut 

 as thin as you can, treat with 95 per cent alcohol for 15 minutes, 50 per 

 cent alcohol for 5 minutes, safranin for 2 hours (or overnight) ; rinse in 

 50 per cent alcohol, 85 per cent for 1 minute, light green for 2 minutes, 

 95 per cent for 10 seconds, absolute alcohol, for 10 seconds, clove oil 

 until clear (a few seconds), xylol, balsam. 



Every preparation of wood should show transverse, longitudinal 

 radial, and longitudinal tangential sections. 



Safranin and Delafield's haematoxylin should show the bars of 

 Sanio clearly, as should also the safranin and crystal violet, or gentian 

 violet. A 50 per cent alcoholic safranin may be allowed to stain for a 

 week ; and crystal violet, either in water or clove oil, may stain several 

 hours or overnight. With care in differentiation, the long periods give 

 splendid results. A little orange in clove oil usually improves the 

 stain. If a preparation shows the bars of Sanio and differentiates the 

 bordered pit, the technique is good (Fig. 116). 



Jeffrey's maceration method will isolate the tracheids and other 

 cells, which can then be stained and mounted in balsam. Be careful 

 to wash out all acid before staining. Such preparations show features 

 which are likely to be overlooked in sections. 



