180 BOTANICAL MICROTECHNIQUE. 



A. Platinum chloride, PtCl 4 . 



311. A \% aqueous solution of platinic chloride has been 

 recommended by Rabl (I, 216) for fixing nuclear figures. 

 Its use brings out especially the longitudinal splitting of the 

 segments of the nuclear thread and the chromatin spheres. 

 It should act, in general, for 24 hours. 



//. Chromic-acid-Platinum-chloride. 



312. Merkel used the following combination : 100 volumes 

 of i% chromic acid, 100 volumes of i$ platinic chloride, and 

 600 volumes of water. This medium renders good service 

 also with vegetable objects. It should act for 24 hours. 



v. Platinum-chloride-Osmic-acetic acid. 



313. F. Hermann (I, 59) has recommended the following- 

 mixture : 15 volumes of a \% platinic chloride solution, one 

 volume of glacial acetic acid, and two or four volumes of 

 2$ osmic acid. Hermann allows this mixture to act from 

 one to two days. To show the achromatic nuclear figure,, 

 he washes the fluid out in running water, hardens in alcohols 

 of increasing strength, and then lays the objects in crude 

 pyroligneous acid for 12 to 18 hours (cf. Hermann, II, 571). 



b. Staining Methods. 

 a. Haematoxylin. 



314. Besides carmine, haematoxylin has been most used 

 for staining nuclei, and we have a great number of recipes 

 for the preparation of specially active haematoxylin solu- 

 tions. Among these the so-called Delafield's hcematoxylirt 

 solution, also often erroneously called Grenacher s haema- 

 toxylin, seems to deserve preference in most cases. It is 

 prepared as follows : 4 grams of haematoxylin are dissolved 

 in 25 ccm. of alcohol, then 400 ccm. of a concentrated 

 aqueous solution of ammonia alum are added, and the mix- 

 ture is allowed to stand in the light for 3 or 4 days and is 

 filtered ; 100 ccm. of glycerine and 100 ccm. of methyl alco- 

 hol are added, the whole is allowed to stand again for a 



