272 



METHODS IN PLANT HISTOLOGY 



Young stages of Cyathus, Crucibulum, and Nidularia cut easily in 

 paraffin; somewhat older stages can be cut in celloidin, but mature 

 stages fail to cut by any of our present methods. 



It is often desirable to secure differential staining of the fungus and 

 its host. Some of the methods previously mentioned secure this result 

 and give excellent detail, but do not make the mycelium stand out 

 sharply in contrast with the tissues of the host. A special method by 



B. T. Dickson generally gives a 

 good differentiation. He uses 

 Magdala red and light green, us- 

 ing the Magdala red in a 2 per cent 

 solution in 85 per cent alcohol, and 

 the light green in a 2 per cent solu- 

 tion in clove oil to which have been 

 added a few drops of absolute al- 

 cohol. His schedule is as follows : 



1. Dissolve paraffin in xylol and 

 wash in absolute alcohol. 



2. Wash in 95 and 85 per cent al- 

 cohol. 



3. Stain with Magdala red 5-10 

 minutes. 



4. Remove surplus stain and wash 

 in 95 per cent alcohol. 



5. Stain in Hght green in clove oil 

 for 1-3 minutes. 



6. Wash in absolute alcohol, or in 

 carbol turpentine. 



7. Clear in xylol and mount in 

 balsam. 



Fig. 75. — Coprinus: young basidia with 

 four nuclei whicli, later, pass into the spores; 

 fixed in chromo-acetic acid and stained in 

 safranin, gentian violet, orange. X780. 



The time factors will vary slightly with different material. If the 

 light green overstains slightly it may not interfere much with the 

 differentiation. Mycelium, spores, amoebae, and bacterioidal tissue 

 stain red, and the host tissues, green. If tissues do not stain readily, 

 mordant in a 1 per cent solution of potassium permanganate in water 

 for 2-5 minutes, wash in water, pass through the alcohols to 85 per 

 cent alcohol, and stain. The mordant does not keep. 



This combination has given good results with the following mate- 

 rial: Plasmodiophora brassicae, legume tubercles, Albugo Candida, 



