ALBINISM, WITH SPECIAL REFERENCE TO SHIRLEY POPPIES. 481 



amongst the plants were some which showed incomplete albinism in the 

 upper portions of their petals, whilst their centres showed lccal albinism, 

 or in a few cases retained the black colour of Papaver Bhceas. 



On cutting sections through the two colour regions I found that the 

 black appearance was wholly caused by a very strong solution of a dark 

 red pigment dissolved in the cell-sap of the epidermal cells on both 

 surfaces of the petals. It is very much the rule that black colours in 

 plants are produced by a dark red or crimson cell-sap overlying cells con- 

 taining abundant chlorophyll. This is how the black blotches on the 

 leaves of Arum macidatum, the black stripes on some of the leaves of 

 Ranunculus Ficaria, and the black colour on the dorsal sepal of Cypri- 

 pedium Boxallii are produced. An exception is Gcelogyne pandurata, 

 where the dead-black colour on the labellum is caused by a gelatinous 

 non-granular pigment-mass which fills the epidermal, and in some places 

 the deeper-lying cells. This is black, reddish-brown, orange, or yellow, 

 according to the thickness of the cell-section obtained, and is a pigment 

 of the xanthic series. 



The pigment in the upper portions of the Poppy petals was also con- 

 tained in solution in the cell-sap of the epidermal cells, but varied in 

 different flowers from a pinkish-red to an orange-red. No especially close 

 search was made for chromoplasts either in these cells or in the under- 

 lying ones, but none were observed, and it is not probable that any are 

 present. 



On applying microchemical tests it was found that the behaviour of 

 the pigments of the two regions in question differed. The following 

 table shows the principal results : 



Reagent 



Black Blotch 



Upper part of Petals 



Concentrated 

 sulphuric acid. 



Pink, then brick-red inclining 

 towards a deep orange. 



From pink to brick-red, then 

 through orange to yellow until 

 the colour is discharged. 



Iodine in 

 potassium iodide. 



In a quarter of an hour the 

 colour had changed to a port- 

 wine tint. No further change. 



The colour slowly faded out 

 without any change of tint. 



Solution of 

 caustic potash. 



At once a very deep blue. 

 Then lighter and lighter, until 

 it bleached out without any 

 change of tint. 



Through green to light 

 greenish -yellow. Slowly then 

 the colour bleached out 

 entirely. 



It thus appears that the pigments are distinct, and this supplies one 

 reason why the one may disappear completely whilst the other may 

 persist. 



Whilst both pigments belong to the cyanic series, neither of them 

 shows the typical reactions of the commonest members of this series. 

 The central black colour is certainly produced by a single-colour sub- 

 stance ; that of the rest of the petal may not impossibly be a mixture of 

 a cyanic with a minute portion of a xanthic pigment, and if that is so it 

 helps to explain the difficulty of getting a completely albino Papaver 

 Bhceas. For it is much rarer to get an albino of the xanthic than of the 

 cyanic pigments. 



