150 



METHODS IN PLANT HISTOLOGY 



Many fixing agents either destroy the mitochondria or make it al- 

 most impossible to demonstrate them. Fixing agents containing al- 

 cohol or any considerable percentage of acid are to be avoided. 



We recommend neutral formalin, with 10 c.c. of formalin to 90 c.c. 

 of distilled water. Get the neutral formalin from commercial formalin 

 by distilling with sodium carbonate. It is not worth while to distil 

 more than you need within the next 24 hours, because the formalin 

 will not remain neutral. Formic acid appears in it and its value as a 

 fixing agent for chondriosomes is at an end. Fix for 48 hours, wash in 

 water, and follow the regular procedure for Haidenhain's iron-alum 

 haematoxylin. The chondriosomes should stain black. 



B 



C 



Fig. 27. — Chondriosomes. A, periblem of root tip of Allium cepa. Fixed in 10 per cent neutral 

 formalin and stained in iron-alum haematoxylin. Preparation by Yamanouchi. B, cells in young 

 megasporangium of Asparagus officinalis. Fixed in formalin chromic acid and stained in iron-alum 

 haematoxylin. Both X1135. C, canaliculi in root tip of Allium cepa, fixed in Bensley's solution 

 and stained in iron-alum haematoxylin. X1200. 



Benda's solution, followed by Haidenhain's iron-alum haematoxy- 

 lin, will give good results. A solution recommended by Bensley is good 

 also for plant material. 



Bensley's solution. — 



Osmic acid, 2 per cent 1 part 



Corrosive sublimate (HgCl,), 2^ per cent 4 parts 



Add 1 drop of glacial acetic acid to 10 c.c. of this solution. Fix for 

 24-48 hours and wash thoroughly in water. On the slide, bleach with 

 hydrogen peroxide; wash in water; treat with the iodine solution used 

 in testing for starch; then wash in water. The shde is now ready for 

 staining. We recommend the usual Haidenhain's iron-alum haema- 

 toxylin. 



