History—In China these galls are probably known and used both medicinally and in dyeing since very long; they are mentioned in the herbal Puntsaou, written in the middle of the 16th century. They also occur in Cleyer’s “Specimen medicinæ sinicæ,” Frankfort, 1682, No. 225, under the name u poi çu.[684] Kämpfer[685] also mentions a tree “Baibokf, vulgo Fusi,” growing on the hills, the pinnate leaves of which he found often provided with an excrescence: “Ἐπίϕνσι foliorum informi, tuberosa, multiplici, tenui, dura, cava, Gallæ nostratis usu praestante.” No doubt this refers to the galls under notice; they began to be imported into Europe about 1724, and are noticed by Geoffroy[686] as Oreilles des Indes, but they seem to have soon disappeared from the market. Pereira directed attention to them in 1844, since which time they have formed a regular and abundant article of import both from China and Japan.
Formation—Chinese galls are vesicular protuberances formed on the leafstalks and branches of the above-mentioned tree, by the puncture of an insect, identified and figured by Doubleday[687] as a species of Aphis, and subsequently named provisionally by Jacob Bell[688] A. chinensis. We have no account by any competent observer of their growth; and as to their development, we can only imagine it from the analogous productions seen in Europe. According to Doubleday, it is probable that the female aphis punctures the upper surface of a leaf (more probably leafstalk), the result of the wound being the growth of a hollow expansion in the vegetable tissue. Of this cavity the creature takes possession and brings forth a progeny which lives by puncturing the inner surface of their home, thus much increasing the tendency to a morbid expansion of the soft growing tissue in an outward direction. Meanwhile the neck of the sac-like gall thickens, the aperture contracts and finally closes, imprisoning all the inmates. Here they live and multiply until, as in the case of the pistacia gall of Europe, the sac ruptures and allows of their escape. This, we may imagine, takes place at the period when, after some generations all wingless and perhaps all female (for the female aphis produces for several generations without impregnation), a winged generation is brought forth of both sexes. These may then fly to other spots, and deposit eggs for a further propagation of their race.
The galls are collected when their green colour is changing into yellow; they are then scalded.[689]
Description—The galls are light and hollow, varying in length from 1 to 2½ inches, and of extremely diverse and irregular form. The simplest are somewhat egg-shaped, the smaller end being attached to the leafstalk; but the form is rarely so regular, and more often the body of the gall is distorted by numerous knobby or horn-like protuberances or branches; or the gall consists of several lobes uniting in their lower part and gradually attenuated to the point by which the excrescence is attached to the leaf.[690] But though the form is thus variable, the structure of these bodi4s is very characteristic. They are striated towards the base, and completely covered on other parts with a thick, velvety, grey down, which rubbed off on the prominences, displays the reddish-brown colour of the shell itself. The latter is ⅒ to ¹/₂₀ of an inch in thickness, translucent and horny, but brittle with a smooth and shining fracture. It is rather smoother on the inner surface and of lighter colour than on the outer.
The galls when broken are generally found to contain a white, downy-looking substance, together with the minute, dried-up bodies of the killed insect.[691]
The drug as imported from Japan is usually a little smaller and paler; it mostly fetches a better price in the market.
Microscopic Structure—The tissue of the galls is made up of thin-walled, large cells irregularly traversed by small vascular bundles and laticiferous vessels. The latter are mostly not branched. The parenchyme is loaded with lumps of tannic matter and starch, the latter having mostly lost by the treatment with boiling water its granular appearance. The epidermis of the galls is covered with little tapering hairs, consisting each of 1-5 cells, to which is due the velvety down of the drug.
Chemical Composition—Chinese or Japanese galls contain about 70 per cent. of a tannic acid, which has been first shown by Stein in 1849 to be identical with that derived from oak galls (see Gallæ halepenses), the so-called gallo-tannic or common tannic acid.[692] It is remarkable that this substance, which is by no means widely distributed, is also present in Rhus coriaria, a species indigenous in the Mediterranean region. Its leaves and shoots are the well-known dyeing and tanning material Sumach.
Stein, however, pointed out at the same time, that in Chinese galls gallo-tannic acid is accompanied by a small amount, about 4 per cent., of a different tannic matter.
Commerce—At present the supplies arrive chiefly from Hankow, from which great trading city the export, in 1872, was no less than 30,949 peculs, equal to 36,844 cwt; 21,611 peculs, value 136,214 taels (one tael about 6s.) in 1874. In 1877 all China exported not more than 17,515 peculs. A little is also shipped from Canton and Ningpo.[693] The quantity imported from China into the United Kingdom in 1872 was 8621 cwts., valued at £20,098. In the China trade returns, the drug is always miscalled “Nut galls,” or “gallnuts.” Only those called “Wu-pei-tze” are the galls under examination. There are also oak galls exported from China resembling those from Western Asia. Japanese galls, “Kifushi,” are shipped in increasing quantities at Hiogo.[694]