132 Methods in Plant Histology 



spermatozoids of the pteridophytes also stain by this method, 

 although not so brilliantly as in case of the cycads. 



The cilia of the motile spores of Thallophytes may often be 

 demonstrated by allowing a drop of the iodine solution used in testing 

 for starch to run under the cover. 



Zimmermann gives the following method: Bring the objects into 

 a drop of water on the slide and invert the drop over the fumes of 1 

 per cent osmic acid for 5 minutes. Allow the drop to dry. Then add 

 a drop of 20 per cent aqueous solution of tannin, and after 5 minutes 

 wash it off with water. Stain in a strong aqueous solution of fuchsin 

 (or carbol fuchsin) for 5 minutes. Allow the preparation to dry 

 completely, and then add a drop of balsam and a cover. The cilia 

 should take a bright red. 



Zimmermann also found the following method satisfactory for 

 the cilia of the zoospores of algae and fungi: Fix by adding a few 

 drops of 1 per cent osmic acid to the water containing the zoospores; 

 then add an equal amount of a mixture of fuchsin and methyl violet. 

 The fuchsin and methyl violet should be 1 per cent solutions in 95 per 

 cent alcohol. In a few seconds the cilia stain a bright red. 



While gentian-violet gives the cilia of cycads a beautiful and 

 brilliant stain, we have found that nothing surpasses Haidenhain's 

 iron-alum haematoxylin in giving clear and definite views of cilia. 



MITOCHONDRIA 



Since the second edition of this book appeared, in 1908, the terms 

 mitochondria, chondriosomes, Chondriokonten, Chondromiten, etc., 

 have become increasingly frequent in botanical literature. These 

 mitochondria, as we shall call them, are minute structures, probably 

 present in most cells, but not differentiated by the most usual 

 methods and generally overlooked when they might be seen. Most 

 of them are as small as bacteria and bear a superficial resemblance 

 to coccus, spirillum, and bacillus forms (Fig. 24, A). 



Many fixing agents either destroy the mitochondria or make it 

 almost impossible to demonstrate them. Fixing agents containing 

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

 Benda's solution, followed by Haidenhain's iron-alum haematoxylin. 



