The problem, then, which plantdistribution presents is twofold: it has first to map out the earths surface into regions or areas of vegetation, and secondly to trace the causes which have brought them about and led to their restriction and to their mutual relations.
His zeal is represented in a twofold aspect.
This twofold development of the idea of God formed the point of leverage for Zoroaster's reformation.
This tautomerism may be of a twofold nature :-(I) it may involve the mere oscillation of linkages, as in acridine; or (2) it may involve the oscillation of atoms, as in fluorescein.
We find a division of social ranks which reminds us of the threefold gradation of Lower Germany (edelings, frilings, lazzen - eorls, ceorls, laets), and not of the twofold Frankish one (ingenui Franci, Romani), nor of the minute differentiation of the Upper Germans and Lombards.