ROYAL BOTANIC GARDENS, KEW 



BULLETIN 



OF 



MISCELLANEOUS INFORMATION. 



No. 2.] 



[1908 



VIIL-MUSEUM PREPARATIONS. 



The Preservation of Green Colours in Botanical 



Specimens Exposed to Light. 



J. W. H. Trail. 



The alteration caused in green parts of plants after exposure to 

 light for some time, whether these are dried or in preservative 



fluids, renders them unsightly, and deprives them of much of 

 their value by obscuring or obliterating the distinction in colour 



between the assimilating tissues and the other parts of the 



specimen. With specimens in fluid, especially when preserved 



in alcohol, it is customary to bleach them until all parts are 



deprived of colour before they are admitted to the shelves of 



museums. Such bleached specimens are indeed preferable to the 



brown ones that are apt to result where alcohol is used without 



previous bleaching; and they have the further advantage, when 



bleached, of not discolouring the preservative fluid. But the 



uniformity of tint, whether brown or colourless, greatly lessens 



the usefulness of even the most carefully prepared specimens, 



especially in an educational museum, and I have sought by 



various methods to preserve the green colours at least sufficiently 



to indicate the important difference in function between the green 



parts and the other organs of plants. The various methods in use 



and the various solutions recommended as preservatives were 



tried, 'and, while partially successful in * certain cases, all were 



unsatisfactory in results, or difficult to employ and liable to fail. 



I had tried acetic acid as a preservative fluid ; and found that 

 although specimens, especially small bodies, such as galls, her- 

 metically inclosed in glass tubes, retained their form in it they 

 became discoloured. The effect of the salts of copper on the colour 

 of vegetables preserved for food was known to me ; but the value 

 of copper as an aid in the preparation of permanent specimens 

 for teaching, and for exhibition in museums, suggested itself to 

 me more clearly after reading Dr. E. Sehunck's papers on the 

 chemistry of chlorophyll. I sought to obtain the formation 

 within the green parts' of the specimens of the compounds of 



1375 Wt«87 2/08 D & S 29 31012 



h.o. Bot. Cardf i 



i9oy 



