"During my recent travels," Dr. Sidney Hickson writes to a scientific contemporary, "I was frequently asked by the Dutch planters and others if I had ever seen 'a cocoa-nut stone.' These stones are said to be rarely found (1 in 2000 or more) in the perisperm of the cocoa-nut, and when found are kept by the natives as a charm against disease and evil spirits. This story of the cocoa-nut stone was so constantly told me, and in every case without any variation in its details, that I made every effort before leaving to obtain some specimens, and eventually succeeded in obtaining two. "One of these is nearly a perfect sphere, 14 mm. in diameter, and the other, rather smaller in size, is irregularly pear-shaped. In both specimens the surface is worn nearly smooth by friction. The spherical one I have had cut into two halves, but I can find no concentric or other markings on the polished cut surfaces. "Dr. Kimmins has kindly submitted one-half to a careful chemical analysis, and finds that it consists of pure carbonate of lime without any trace of other salts or vegetable tissue. "I should be very glad if any of your readers could inform me if there are any of these stones in any of the museums, or if there is any evidence beyond mere hearsay of their existence in the perisperm of the cocoa-nut." [346] On this letter Mr. Thiselton Dyer makes the following remarks:--"Dr. Hickson's account of the calcareous concretions occasionally found in the central hollow (filled with fluid--the so-called 'milk') of the endosperm of the seed of the cocoa-nut is extremely interesting. It appears to me a phenomenon of the same order as tabasheer, to which I recently drew attention in Nature. "The circumstances of the occurrence of these stones or 'pearls' are in many respects parallel to those which attend the formation of tabasheer. In both cases mineral matter in palpable masses is withdrawn from solution in considerable volumes of fluid contained in tolerably large cavities in living plants; and in both instances they are monocotyledons. "In the case of the cocoa-nut pearls the material is calcium carbonate, and this is well known to concrete in a peculiar manner from solutions in which organic matter is also present. "In my note on tabasheer I referred to the reported occurrence of mineral concretions in the wood of various tropical dicotyledonous trees. Tabasheer is too well known to be pooh-poohed; but some of my scientific friends express a polite incredulity as to the other cases. I learn, however, from Prof. Judd, F.R.S., that he has obtained a specimen of apatite found in cutting up a mass of teak-wood. The occurrence of this mineral under these circumstances has long been recorded; but I have never had the good fortune to see a specimen." [347] The Durian