464 M. Wheldale. 



C. More rarely white flowers become red and tinged flowers 

 deeper in colour. 



As a rule the results of autolysis cannot be predicted; but as 

 in the case of the oxydase reaction, if bruising' causes discolouration, 

 autolysis will produce a brown colour. The same result may be 

 brought about by crushing the plant in a mortar and sometimes by 

 immersion in absolute alcohol. There is undoubtedly some intimate 

 connection between the appearance of this brown colouration and the 

 oxydase activity of the plant ; for positive results with oxydase tests 

 always accompany browning on autolysis, whereas plants which only 

 show changes in anthocyanin colour, do not as a rule give strong 

 oxydase reactions. Death, or injury to the protoplasm, caused by 

 treatment with chloroform or immersion in alcohol, must in some way 

 release the oxydase from the bonds of the inhibitive factors which 

 regulate the activities of oxydising enzymes in the living tissue. 

 The result is a rapid transference of oxygen to oxidisable bodies in 

 the cell-sap and an immediate production of brown pigment. 



Cases of post-mortem production of pigments comparable to these 

 autolytic changes are those of the indigo-producing plants, Indigofera, 

 Isatis, etc. Indigo, as is well known, results from the action of an 

 oxydase, indicase, upon a chromogen, indican; moreover the pigment 

 is not produced in the uninjured plant. Another interesting case and 

 one which has been worked out in detail by Miss Tammes ^), is that 

 peculiar to the Dipsaceae. In genera of this order, a blue pigment, 

 dipsacotin, is the oxidation product of an enzyme, dipsacase, acting 

 upon a colourless chromogen, dipsacan. Miss Tammes has shown 

 that the pigment is only formed after death and then a raised tem- 

 perature between 35 "^ — 100^ C is also essential. Yet another remar- 

 kable instance is that described by M o 1 i s c h -) for ScliencMa blumena- 

 viana, a species of Rubiaceae. The plant is normally green with white 

 flowers but injury or the action of chloroform vapour immediately 

 induces the formation of an intensely red pigment. 



The significant point in connection with the above phenomena 

 is that the pigments resulting after death are never formed in living 

 healthy tissue. The most reasonable inference is that post-mortem 

 pigments are the abnormal products of oxydases, of which the activities 

 are directed towards another end, during the life of the plant. It is 

 otherwise inconceivable that some metabolic disturbance should not 

 give rise to indigo, dipsacotin, etc., as the case may be, in the living 

 plant. 



^) Dipsacan iiiid Dipsacotin, ein neues Chromogen und ein neuer Farbstoff der 

 Dipsaceae. Extrait du Recueil des Travaux botaniques Néerlandais, Vol. V. 1908. 



^) Über ein neues, einen karminroten Farbstoff erzeugendes Chromogen bei 

 Schenckia blumenaviana. Ber. d. d. bot. Gesell. 1901. 



