98 Green. — On Vegetable Ferments. 
crease of them inhibits the secretion. Marshall Ward noted a 
similar fact in his experiments with Botrytis. 
Pectase. One of the earliest known ferments of the vegetable 
organism was described by Fremy in 1849 1 . He says that 
the cell-wall is largely composed of a substance to which he 
gives the name of pectose, which differs from cellulose in many 
of its reactions. Pectose, or pectin, by®the action of an enzyme 
existing in certain cells, can be converted into two gelatinous 
bodies, pectosic and pectic acids. The transformation proceeds 
by two stages, the two acids being formed successively. They 
differ from pectin chiefly in the amount of water they contain. 
Pectase, as Fremy calls the ferment, exists in two conditions 
in the vegetable organism ; from the carrot and the beet it can 
be extracted by mashing the roots and expressing the juice 
from the pulp ; in acid fruits it exists in an insoluble condition. 
If juices of the pulp of these be put into a solution of pectin, 
they cause a very rapid gelatinisation, forming as before 
pectosic and later pectic acid. From the juice of young carrots 
pectase can be precipitated by alcohol. Its optimum working 
temperature is 30° C., and it is destroyed by prolonged boiling. 
It can work in the absence of oxygen. 
A ferment of this kind is described by Wiesner 2 as obtain- 
able from gum-arabic. He speaks of it as transforming 
cellulose into gummy or mucilaginous substances. Reinitzer 3 
denies the cellulose-transforming power, and says that the 
ferments extractable from gum are diastatic. 
Glucoside-Enzymes. 
The next group of ferments that we shall consider are 
somewhat like the foregoing in that they aid in furnishing 
the plant with a supply of soluble diffusible carbohydrate 
material in the form of sugar. They differ however in their 
1 Ann. Chim. et Phys., Ser. 3, vol. XXIV, p. 1. 
2 Wiesner, Sitzungsb. d. k. Akad. d. Wissensch. in Wien, xcii, p. 140: also 
Bot. Zeitg., 1885. 
3 Reinitzer, Ueber die wahre Natur des Gummifermentes, Zeitschr. f. Phys. Chem. 
1890. 
