SITE OF PHOSPHATASE IN NUCLEI 59 



minutes' exposure to 95 percent alcohol causes the destruction 

 of practically the whole of the phosphatase of the nuclei of 

 onion and bean root tips. By working rapidly, however, it 

 has been possible to squash root tips in 80 percent alcohol, re- 

 move the cover slip immediately under 95 percent alcohol, allow 

 up to 30 seconds for fixation in the 95 percent alcohol, and then, 

 after removal to distilled water, find some phosphatase still 

 present in the nuclei. For the demonstration of alkaline phos- 

 phatase in plant nuclei three methods have been successful: the 

 method of Takamatsu and Gomori, using glycerophosphate as 

 substrate; the use of /?-naphthol phosphate as a substrate; and 

 the use of the dye phosphate of Loveless and Danielli as a sub- 

 strate. Plate X, Fig. A, shows an onion root tip, with glycero- 

 phosphate as substrate; Fig. B shows the distribution of phos- 

 phatase in an onion root tip, with /?-naphthol phosphate as sub- 

 strate. 



It is clear that, whereas the physical properties of the enzyme 

 found in plant tissues and plant-tissue nuclei may differ con- 

 siderably from those of the animal enzyme, this enzyme is, 

 nevertheless, found in plant nuclei, and that it therefore may 

 well have as general a significance in nuclear processes as has 

 deoxypentose nucleic acid. 



The Details of the Distribution of Alkaline Phosphatase 

 in Nuclei 



Considerable caution must be exercised in the interpretation 

 of the detailed distribution of phosphatase in cell nuclei, par- 

 ticularly when the nuclei are small, or as far as the finer details 

 are concerned. When one is concerned with large structures 

 such as the bands of Drosophila chromosomes, or with the dis- 

 tinction between chromosomes and nucleoli, the method for the 

 detection of diffusion artefacts given earlier in this chapter is 

 quite adequate. I am by no means convinced that it is pos- 

 sible to interpret the detailed picture of apparent phosphatase 

 distribution found with the individual chromosomes of normal 

 somatic tissues, even when full use is made of the critical meth- 

 ods at present available. 



When the methods of analysis of the extent to which diffusion 

 artefacts are present cannot be used, interpretation becomes 

 much more hazardous. This is the case, for example, in tissue 



