In this mushroom, for which, as we have seen, the _Amanita_ is too frequently mistaken, the inside as well as the outside is yellow; the upper surface of the pileus, which is equally free from scales and warts, is, however, of a reddish yellow, like that of an orange (whence the popular French name, _la vrai oronge_); all the other parts are of a beautiful citron hue. This agaric exhales an agreeable odour, combined apparently of the scent of the vanilla and the truffle. It decomposes rapidly, and when in a state of advanced putridity, the fragrance I speak of is succeeded by--well, by a fearful stench! When young, and still completely covered with its wrapper or _volva_ (this, in the _Amanita_, is imperfect), it is very like a hen's egg which has been partly buried in the ground so as to expose only the larger end. It seems partial to solitude; more than four or five are seldom found in the same locality. Moreover, in autumn it affects the same habitats as the _Amanita_,--which is unfortunate. It would seem that our imperial mushroom was specially appreciated by the ancients, and it is said that Nero pronounced it a dish fit for the gods. In this circumstance originated the scientific name which has now become popular, and which was first applied to it by the cryptogamist Fries, _Agaricus Cæsareus_. [Illustration: FIG. 74.--The Imperial Mushroom.] * * * * * The _Boletus_ of Pliny appears to have been our Agaricus, and not one of our _Boleti_, which are easily recognised by the numerous tubercular projections covering the under part of the pileus. In proof of this I would point out that the Roman naturalist, after speaking of the _Boleti_ as genuine delicacies, immediately inveighs against them as dangerously poisonous. He relates that it was with one of these, or rather with one of the false mushrooms so easily mistaken for the true, that Agrippina poisoned the Emperor Claudius, to secure the imperial crown for her son Nero.[81] The virtues of the mushrooms have been sung by Juvenal and Martial. The latter accurately distinguishes the true from the false, when reproaching Cæcilianus with his gluttony. "Ah, you are used to devour your _Boleti_ alone, in the face of your invited guests; eat then, the _Boletus_ which Claudius ate!" "Dic mihi, quis furor est? Turba spectante vocata, Solus boletos, Cæciliane, voras. Quid dignum tanto tibi ventri, gulaque precabor? Boletum, qualem Claudius edit, edas."[82] The best known and most valuable species of Agarici may be briefly enumerated:-- _Agaricus campestris_, or _Common Mushroom_, found in nearly all temperate regions: pileus convex, and white, with a tinge of brown; thick set on the under side with dark brown gills; stem firm and fleshy, and surrounded by a white membranous ring. _Agaricus Cæsareus_, or _Imperial Mushroom_, the _Kaiserling_ of the Germans, already described.