256 VEGETABLE PHYSIOLOGY 



takes place in the plant is uncertain, but it is clear that the 

 starch, which is insoluble, is converted into sugar, which 

 can be removed to the parts of the plant where it is required 

 for building up the protoplasm. 



Inulase occurs in the tubers and tuberous roots of some 

 of the Composite, in the bulbs of certain Monocotyledons, 

 and in some of the Fungi. It converts inulin ultimately 

 into levulose or fructose, but the action is not a very simple 

 one, at least one intermediate body being formed during 

 the process. 



Invertase has a much wider distribution. It is easily 

 extracted from the Yeast-plant, in which it is present in 

 relatively considerable quantity. Other fungi which con- 

 tain it are Fusarium and Aspergillus, besides certain bacteria. 

 In flowering plants it has been found in seeds, buds, leaves, 

 stems, roots, and pollen grains. Its action is the hydrolysis 

 of cane-sugar, which it splits up into glucose and fructose, 

 according to the equation 



C 6 H 12 6 + C 6 H 18 O fl 



Cane-sugar Water Glucose Fructose 



Glucase occurs in the grains of various cereals, being 

 especially prominent in the Maize. It is also fairly abundant 

 in the Yeast-plant. It has no action on cane-sugar, but 

 splits up maltose into glucose, one molecule of the former 

 taking up water and yielding at once two molecules of 

 the latter. 



Other sugars of similar constitution to maltose and 

 cane-sugar are made to undergo similar transformations by 

 enzymes of less widespread distribution. The chief of these 

 are trehdlase, raffinase or melibiase, melizitase, and lactase. 



There appear to be several varieties of cytase, which 

 can be prepared from various seeds. The enzyme was 

 first discovered in the germinating grain of the barley, in 

 which it is located chiefly in the aleurone layer and to a 

 less extent in the epithelium of the scutellum, where it 

 exists side by side with diastase. It dissolves the walls of 



