1887-88.] Colouring Matters of Leaves and Flowers. 285 



Lapraik were led to judge that the change was of a 

 molecular, not of a chemical nature. Such changes may 

 be observed by any one with the simplest experimenting. 

 I may instance a few of such changes observed last summer 

 by Mr Terras — the isolated instances elsewhere recorded 

 being in no way more instructive. 



The commonest transitions were those in accordance with 

 the ordinary litmus-reactions of acid or alkalies ; a seeming 

 exception (doubtless due, however, to the action of the acid 

 on the protoplasm of the corpuscle) being where a fixed red 

 changed to a dirty blue with H2S0^ and HNO3. Fluid- 

 yellows of CEnotlura, Alyssum, Cheirantlms, were changed to 

 blue by H2SO4, by HNO^, by solution of I and KI. The 

 yellow of Verbasntm failed to give any reactions, whilst 

 many fixed yellows gave those of chlororufin. The yellow 

 of Linaria changed to bright red with H^SO^. The red of 

 Dianthus ddtoides changed to yellow with H2S0^, and as 

 with KHO, this yellow changed back to a transitory red 

 with acids. 



From some experiments which I made with a strong 

 solution of KHO, I was able to detect some method among 

 the number of such changes observed by myself and corro- 

 borated by many of the instances given by others. 



It is known that chlorophyll becomes yellow by the 

 action of alkalies ; similarly I found that any other colour 

 might be reduced to the same kind of yellow by the same 

 means. Eeds of Linuni, Monarda, and Diantlms; blues of 

 Myosotis, Campanula, and Salvia; whites of Viola, Vaccinium, 

 and Campamda, were finally all rendered yellow. The yellow 

 appeared after a longer or a shorter time ; but it was re- 

 markable that whilst the whites passed directly to yellow, 

 the blues passed through a transitory emerald -green stage, 

 due of course to the mixing of these colours ; the reds 

 became blue, then green, but in the end yellow as the others. 



It is apparent that such easily-induced changes need more 

 careful observation and more definiteness of experiment, 

 before even such a transition to yellow as this above noticed 

 can indicate anything to us with certainty. It is essential 

 in all such cases to know as to the strength of the reagent — 

 varying results being given with solutions of different 

 strength in the same space of time. 



