MECHANISM OF CHEMICAL CHANGES 163 



the organism causing cabbage black rot, which softens the 

 middle lamella over large areas of the leaf causing the cells 

 eventually to die and decompose. 



Among the higher plants the most common reserve carbo- 

 hydrate materials stored up are starch and inulin. Starch 

 is a polymer of dextrose, inulin a polymer of levulose. 

 Starch is attacked or hydrolyzed by the enzyme amylase 

 (diastase) which changes it into dextrin and finally into 

 the sugar maltose (CijHggOii). This enzyme is produced 

 by sprouting seeds, is present in most leaves and growing 

 tissues of plants, and is formed by many species of bacteria 

 and molds, though, so far as is known, not by any of the 

 yeasts. The property of amylase production or starch 

 digestion may be demonstrated with molds or bacteria by 

 the use of starch plates, that is, by plates poured from agar 

 containing dissolved or suspended starch. Those organisms 

 which digest the starch will change its appearance from 

 milky or opaque to transparent and clear. The ability to 

 saccharify or liquefy starch possessed by certain molds has 

 been made use of in industries to prepare starchy materials 

 for alcoholic fermentation by yeasts. These will be dis- 

 cussed later. It should be noted that not all organisms 

 which attack starch and break it down into simple com- 

 pounds, change it into the intermediate simple sugars. For 

 example, the Bacterium aerogenes, although it is able to 

 produce gas and acid in starch solutions, does not develop 

 the enzyme amylase. 



The carbohydrate inulin is very common as a reserve food 

 product in the plants belonging to the sunflower or com- 

 posite family. The sunflower plant itself, chicory, dande- 

 lion and dahlia all contain considerable amounts of this car- 

 bohydrate. The enzyme inulase converts (by hydrolysis) 

 inulin into levulose. Certain molds are known, which pro- 

 duce inulase. "Whether or not this is also produced by 

 bacteria has not been adequately demonstrated. There are 



