All[1] the glandiferous trees produce the gall-nut as well: they only bear acorns, however, in alternate years. The gallnut of the hemeris[2] is considered the choicest of all, and the best adapted for the preparation of leather: that of the latifolia closely resembles it, but is somewhat lighter, and not by any means so highly approved. This last tree produces the black gall-nut also—for there are two varieties of it—this last being deemed preferable for dyeing wool.

(7.) The gall-nut begins to grow just as the sun is leaving the sign of Gemini,[3] and always bursts forth in its entirety in a single night.[4] The white variety grows, too, in a single day, but if the heat happens to overtake it, it shrinks immediately, and never arrives at its proper size, which is about that of a bean. The black gall-nut will remain green for a longer period, and sometimes attains the size of an apple[5] even. The best kind is that which comes from Commagene,[6] and the most inferior are those produced by the robur: it may easily be tested by means of certain holes in it which admit of the passage of the light.[7]