468 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



subsequently, by the decomposition of its chlorophyll, or by the develop- 

 ment of a new pigment or pigments, of a yellow, orange, or orange-red 

 colour, become a chromoplastid. This has been proved to be often, and 

 is probably always, the course of development of chromoplastids. 

 Courchet * followed their development in the flowers of Genista tinctoria, 

 Helianthemum vulgar c, Cacalia cocci?iea, many Cruciferce, Bcrberidea, 

 and others, and found that the plastids were first uncoloured, then green, 

 then yellow, and when development went further, as in Cacalia coccinea, 

 orange-yellow, and finally orange-red. 



Plastids follow an almost independent life in the cells of plants, 

 increasing in number by division of pre-existing plastids, and never being 

 formed de novo from the protoplasm of the cells. The very rare absence 

 of chromoplastids from the flowers of a variety which normally contains 

 them has no ill effects on the plant or its flowers. They are heritable and 

 inherited, and are more rarely found wanting in the progeny of chromo- 

 plastid-containing parents than any other pigment. On the other hand, 

 the production of a plant containing chromoplastids in its flowers from 

 parents wanting these bodies is hardly thinkable. 



Tfye vast majority of yellow, orange-yellow, orange, or orange-red 

 flowers owe their colours to the presence of chromoplastids in the cells. 

 Occasionally the chromoplastid is uniformly coloured by a pigment evenly 

 distributed throughout it, but in most cases the pigment occurs in the 

 plastid in the form of small amorphous granules, or of small crystals. It 

 is possible that the granules may be composed of more than one substance ; 

 the crystals are pure and are composed of a substance called carotin, 

 because first prepared from the root of the Carrot, which owes its colour 

 to this pigment. 



There is carotin in the corona of Narcissus poetic us in the form of 

 rhombohedral plates of a carmine-red colour, in the root of the Carrot 

 and the fruit of the Tomato also in crystal form, as amorphous particles 

 in the fruits of Arum and Taxus baccata, and in a great number of 

 flowers as well as other fruits. It appears to be always present in 

 chlorophyll corpuscles. Arnaud t extracted it from the leaves of Spinach, 

 and found that it formed flat rhombic crystals with a metallic lustre ; that 

 they were dichroic, being greenish-blue in reflected light and orange-red 

 in transmitted light ; and that it is dissolved in concentrated sulphuric acid 

 to a blue solution which was at first momentarily violet. He found that 

 it was a hydro-carbon, and gave to it the formula C 26 H 38 . The pigment 

 extracted by him from Carrots was identical with this. According to 

 Immendorff, the development of carotin is the cause of the autumnal 

 coloration of leaves. + From the corona of Narcissus Tazetta, 1 Grand 

 Soleil d'Or,' carotin with other pigments may be extracted by strong 

 alcohol, and on the evaporation of the solvent the carotin first separates 

 out in the form of orange-red crystals. From solutions in ether the 

 crystals are blood-red. The solution in alcohol is yellow to orange, 

 according to concentration ; the ether solution, in which carotin is more 

 soluble than in alcDhol, is of a deeper orange colour. Carotin is also 



* Courchet, "Reclierches sur les Chromoleucites,'' Ann. des Sci. Naturelles, serie 7. 

 t Arnaud, Comptes Rendus, 1886, p. 751 ; 1886, p. 1119. 

 J Zimmermann, Botanical Micro-technique, p. 102. 



