(from Gr. xXcopos, green, 4nXXov, a leaf), the green colouring matter of leaves. It is universally present in growing vegetable cells. The pigment of leaves is a complex mixture of substances; of these one is green, and to this the name, originally given in 1817 by Pelletier and Caventou, is sometimes restricted; xanthophyll (Gr. avOos, yellow) is dark brown; carotin is copper-coloured. Chlorophyll is related chemically to the proteids; a decomposition product, phylloporphyrin, being very closely related to haematoporphyrin, which is a decomposition product of haemoglobin, the red colouring matter of the blood. Chlorophyll is neutral in reaction, insoluble in water, but soluble in alcohol, ether, &c., the solutions exhibiting a green colour and a vivid red fluorescence. Magnesium is a necessary constituent. (See S. B. Schryver, Science Progress, 1909, 3, p. 425.)