We ought to place the ferula[1] also in the number of the exotics, and as making one of the trees. For, in fact, we distinguish the trees into several different kinds: it is the nature of some to have wood entirely in place of bark, or, in other words, on the outside; while, in the interior, in place of wood, there is a fungous kind of pith, like that of the elder; others, again, are hollow within, like the reed. The ferula grows in hot countries and in places beyond sea, the stalk being divided into knotted joints. There are two kinds of it; that which grows upwards to a great height the Greeks call by the name of "narthex,"[2] while the other, which never rises far from the ground, is known as the "narthecya."[3] From the joints very large leaves shoot forth, the largest lying nearest to the ground: in other respects it has the same nature as the anise, which it resembles also in its fruit. The wood of no shrub is lighter than this; hence it is very easily carried, and the stalks of it make good walking-sticks[4] for the aged.