284 LEAVES 



phyll and probably decomposition products of chlorophyll, are 

 carotin (C4oH 56 ) and xanthophyll (C^H^A), which are usually 

 yellow or orange. Carotin is so named because of its abundance 

 in the root of the Carrot. These pigments are present in fruits, 

 flowers, and autumn leaves, where they produce the yellow and 

 orange colors. Anthocyan, a pigment whose formula is not well 

 known, occurs dissolved in the cell sap and is the basis of the 

 reds, purples, and blues in plants, being red when the cell sap is 

 acid and blue when alkaline. Besides having an important place 

 in determining the color of flowers and fruits, it often occurs in 

 leaves and 'stems. 



In addition to the manufacture of food, which is the function 

 of chlorophyll, the pigments, by producing the showy colors of 

 flowers, assist in pollination. They also add to the attractiveness 

 of fruits and thereby assist in the dissemination of seeds. Often 

 the yellow, red, and blue pigments are prominent in leaves and 

 other structures where they seem to have no function. 



The enzymes are of many kinds and most of the . metabolic 

 changes in cells involve the action of enzymes. They are the 

 most general secretions of protoplasm and - in all living cells 

 enzymes of some kind are present. So far as chemical analyses 

 have been able to determine, they are similar to proteins in 

 composition. They occur dissolved in the cell sap or in intimate 

 relation with the protoplasm, but often diffuse out of the cell and 

 attack surrounding substances. 



Enzymes are specific in their action and hence there are almost 

 as many kinds of enzymes as there are kinds of substances to be 

 acted upon. There is a class of enzymes which acts on proteins, 

 one that acts on carbohydrates, and another that acts on fats. 

 In addition there are enzymes which act on glucosides and other 

 substances of minor importance. The enzymes, called proteases, 

 which act on proteins in plants, are of two classes ereptases and 

 peptases. Peptases have been found in a number of plants but 

 they are not so generally present as the ereptases are. Ereptases 

 apparently break up proteins more completely than the peptases 

 do. Bromelin found in the Pineapple and papain in the Papaw 

 (Carica papaya) are two well known peptases. Papain is used 

 in making digestive tablets. The proteases break the proteins 

 into soluble forms, such as proteoses, peptones, and amino- 

 compounds, that can be translocated and used as food. 



