284 LEAVES 
phyll and probably decomposition products of chlorophyll, are 
carotin (CaoHss) and xanthophyll (CaoHss02), 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. 
