208 QUARTZ FAMILY. Lenz affirms, that the calcedony found in the amygda loid of Deuxponts contains musci of different kinds, such as lichen rangiferinus, conferva;, byssi, and brya. And Blumenbach says, in a letter to Baron Von Moll, that though he had hitherto disbelieved the occurrence of ve getable bodies in the dendritic variety of calcedony named mocha-stone, he must now admit that it does sometimes contain plants, apparently of the nature of conferva. He observed these in specimens from Iceland and Cathe- rinenburg. The same celebrated naturalist found, in the interior of an agate, the fructification of an unknown plant, somewhat resembling the sparganium erectum. Dr Macculloch informs me, that, after examining several hundred specimens of mocha-stone, he is of opinion that they contain cryptogamous plants. '' Observations. 1. Its dull and even fracture distinguish it from Flint; and the same characters distinguish it from Cor nelian. 2. It passes into Opal and Flint; probably also into Si liceous Sinter and Hyalite. 3. It was first accurately described by Werner. 4. The name of this subspecies is by some said to be derived from a town in Asia Mipor, named Chalcedon, where it w r as collected by the ancients. 5. The dendritic variety is supposed to have been ori ginally brought from Arabia, by the way of Mocha; and hence the name Mocha-stone given to it by jewellers. 6. The following are the names given to the different varieties of calcedony by antiquaries and collectors. a. Onyx, where white or grey stripes alternate with brown. b. Chalcedonyxf