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 
CygH0 + HO = CgH,0g + OgHi,0¢ 
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 trehalase, raffinase or meltbiase, 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 
