The Celloidin Method 89 



slides labeled and boxed. Refer to Fig. 6.() lor suggestions on the 

 selection of cover glasses of suitable size. 



The foregoing method is raj)id, highly productive, and entirely 

 satisfactory with materials that do not curl during the staining process. 

 It is often possible to stain at least 50 sections in a Petri dish or 

 evaporating dish and to mount most of the sections before appreciable 

 brittleness and curling develop. Sections that undergo rapid curling 

 after removal of the matrix nuist be handled by other methods. 

 Terpineol has the valuable property of clearing stained and 

 dehydrated sections without making them brittle and without 

 affecting the stain. The terpineol is introduced in place of carbol- 

 xylene. Sections may be lifted singly from terpineol, rinsed in xylene, 

 and promptly mounted. If sections curl with this method, remove 

 the sections singly from terpineol and place them lined up in rows on 

 a dry slide until the slide is filled. Place the sections with the concave 

 side down, and keep them moistened with terpineol. Cover with 

 another dry slide. Place the slides with the pressed sections into a dry 

 Petri dish, and flood with xylene. After 4 to 8 hr. the sections will 

 become hardened flat, and they can be floated out a few at a time, 

 rinsed in two changes of xylene, and mounted in resin before serious 

 curling occurs. 



The foregoing staining process, using a self-mordanting hema- 

 toxylin and safranin, is but one of the many stain combinations that 

 can be used for celloidin sections. Safranin is almost invariably one 

 component, because of the highly lignified character of most plant 

 subjects for which the celloidin method is used. The safranin and fast 

 green combinations yield strikingly beautiful preparations with many 

 subjects. A batch of blue ash stem, killed in FAA showed highly 

 differential, clear and brilliant tones, whereas a batch of red elm, 

 similarly processed, had an unattractive, hazy blue tone in tissues that 

 should have stained green. This stain combination can be tested 

 rapidly with a few sections from any subject and deserves a trial. 

 Follow the sequence given in Staining Chart V, observing the 

 precautions and modifications necessary with celloidin sections. 



Iron hematoxylin is an important stain for celloidin sections, 

 because of its sharp selectivity for the middle lamella. The secjuence is 

 the same as in Staining Chart VI, but the time in mordant and stain, 

 respectively, need not exceed 1 hr. After the stain has been 

 differentiated, washing in water must be very thorough because woody 

 tissues retain the alum tenaciously, resulting in early fading of the 

 stain in the finished preparation. 



