The following typographic errors have been fixed:
Page [20]—servicable amended to serviceable—"... both exogenous and endogenous, render them extremely serviceable to mankind."
Page [21]—organisable amended to organizable, for consistency—"... indeed gum is that organizable product which exists most universally ..."
Page [23]—productivenes amended to productiveness—"... of which there are several varieties, differing essentially in productiveness, ..."
Page [23], fourth footnote—Hedwiz amended to Hedwig—"Eheu qualia! Hedwig."