PEOF. H. M. WAED AND MISS E. DALE ON CRATEROSTIGMA PUMILIJM. 353 



colour in Chammdorea a blue-greea colour before becoming yellow, and, according to 

 Courchet, that in Aloe also first becomes green. Tliis reaction is a very remarkable one 

 to watch, as the change is so rapid that, as the reagent penetrates the tissues, a wave of 

 colour passes over the field, changing and disapj)earing as soon as it is formed. 



Optical Troperiies of the Pigment. 



Tiie granules were examined by means of polarized light, both in the fresh plant and 

 in the residue which remained after evaporation of the alcoholic extract. The granules 

 thus obtained differed little, if at all, from those in the fresh root. Owing to their 

 extremely small size, nothing definite could be determined about them, but they appeared 

 not to be crystalline *. 



We do not think that the colouring-matter occurs in drops in the plant, because the 

 solid granules which are obtained from the alcoholic extract seem to be identical with 

 those in the fresh tissues. 



We have also applied the tests for tannin, but with negative results. 



We therefore regard the cAddence as being against the possibility of the colouring- 

 matter being an oily or resinous body in drops, and it is certainly against its being a 

 crystalline substance allied to carotin. It appears to be present in the form of rounded 

 non-crystalline granules w^hich may possibly be resinous, and which in their micro- 

 chemical reactions most closely resemble the colouring-matter in the flowers of Aloe. 



When the plant is placed with its roots in water and exposed to the action of light, 

 the red colour, even after an interval of some weeks, changes very little. And this 

 apparent fading may be due to the change of the leucoplasts into chloroplasts, and the 

 consequent influence on the colour of the root as a whole ; in solution, however, the 

 colour slowly fades in the light. 



The place of origin of the pigment may now^ be considnred. Courchet has shown 

 that solid pigments are usually, if not always, formed by plastids ; and this fact, taken in 

 connexion with the presence of such plastids in the tissues which contain the colour, 

 points to the origin of the pigment in these bodies, although we have never seen any of 

 the colouring-matter within the cells of our plant. 



Any suggestion that the granules may be bodies foreign to the plant, and of the nature 

 of bacteria, is rendered impossible on account of their complete solubility in more than 

 one reagent, and also because they occur in spaces which are usually closed and have 

 therefore no connexion wdtli the exterior. 



The excretion of colouring-matter by both plants and animals is not an uncommon 

 phenomenon. Such cases of the excretion of carotin are recorded by Zopf . Zimmermann 

 (' Botanical Microtechnique,' English edition, p. 112) mentions the excretion of colouring- 

 matter (which may be crystalline or, more rarely, amorphous) by various lichens. 



As to the possible uses of the pigment we can offer no definite suggestions. It may 



* The colouring-matter of Aloe^ which resembles that in our plant, also occurs in distinct granules which are non- 

 crystalline, and it has not yet been obtained in a crystalline form. 



