40 



Methods in Plant Histology 



great popularity because it was used in Strasburger's laboratory at 

 Bonn. It was the influence of this school and its great master 

 which led to the adoption of the short schedule in the second edition 

 of this book. A few years' trial showed the weakness of the method, 

 and we returned to the longer schedule. The crudeness of the 

 short schedule is doubtless responsible for the tenacity with which 

 the Bonn school has clung to the theory of linin and chromomeres. 

 The young investigator should be warned that during the last 

 twenty years of his life, Strasburger, who had been a leader in 



FIG. 14. A convenient arrangement of staining-dishes. 



technic, cut very few sections and did practically no staining, but 

 used preparations made by assistants. 



Let us now consider a few of the most important stains. 



THE HAEMATOXYLINS 



The most important haematoxylins are Haidenhain's iron-alum 

 haematoxylin, Delafield's haematoxylin, Mayer's haem-alum, and 

 Boehmer's haematoxylin. 



All the haematoxylins mentioned contain alum, and, according 

 to Mayer, who has written the most important work on haematoxylin 

 stains, 1 "the active agent in them is a compound of haematin with 

 alumina. This salt is precipitated in the tissues, chiefly in the nuclei, 

 by organic and inorganic salts there present (e.g., by the phosphates), 

 and perhaps also by other organic bodies belonging to the tissues." 

 These salts are fixed in the tissues by the killing and fixing agent, 

 and when the stain is applied a chemical combination results. 

 Haematoxylins stain well after any of the fixing agents described in 



1 " Ueber das Farben mit Hamatoxylin," Mittheilungen aus der Zoologischen Station zu 

 Neapel, 10 : 170-186, 1891, and "Ueber Hamatoxylin, Carmin und verwandten Materien," 

 Zeitschrift fur wissenschaftliche Mikroscopie, 16:196-220,1899. 



