250 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 Composit, in the bulbs of certain Monocoty- 
ledons, 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,,H,.0,, + H,O = C,H,,0, + C,H,,0, 
Cane-sugar Water Glucose Fructose 
It is a little difficult to understand why this decomposition 
of cane-sugar is necessary, as it can diffuse through 
membranes, and in many cases it has been found capable 
of assimilation by the protoplasm. Probably, however, 
each of the sugars concerned in the transformation has a 
special part to play in the metabolism of the plant, and 
neither can readily replace either of the others. 
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, melibiase, melizitase, and lactase. - 
