We ought to place the ferula982 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,”983 while the other, which never rises far from the ground, is known as the “narthecya.”984 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-sticks985 for the aged.