This section is from the book "Our Edible Toadstools and Mushrooms and How to Distinguish Them", by W. Hamilton Gibson. Also available from Amazon: Our Edible Toadstools And Mushrooms And How To Distinguish Them.
This "poison-cup" may be taken as the cautionary symbol of the genus Amanita, common to all the species. Any mushroom or toadstool, therefore, whose stem is thus set in a socket, or which has any suggestion of such a socket, should be labelled "poison"; for, though some of the species having this cup are edible, from the popular point of view, it is wiser and certainly safer to condemn the entire group. But the cup must be sought for. We shall thus at least avoid the possible danger of a fatal termination to our amateur experiments in gustatory mycology; for, while various other mushrooms might, and do, induce even serious illness through digestive disturbance, and secondary, possibly fatal, complications, the Amanita group are now conceded to be the only fungi which contain a positive, active poisonous principle whose certain logical consequence is death.
Another structural feature of the Amanita is shown in the illustration, but has been omitted from the above consideration to avoid confusion. This is the "veil" which, in the young mushroom, originally connected the edge of the cap, or pileus, with the stem, and whose gradual rupture necessarily follows the expansion of the cap, until a mere frill or ring is left about the stem at the original point of contact. But this feature is a frequent character in many edible mushrooms, as witness the several examples in the edible species of our plates, and therefore of no dangerous significance per se, being merely a membrane which protects the growing gills.
Nor are the other features, the remnants of the volva on the summit of the cap, to be considered of primary importance from the popular point of view, for the reason - firstly, that these fragments, while conspicuous and constant in Amanita muscarius (Plate 4), are not thus permanent in several other species of Amanitae, notably the white-satin-capped Amanita vermis, Amanita phailoides, and Amanita Caearca, in which the fragments are deciduous; and, secondly, because the same general effect of these warty scales is so clearly imitated in other mushrooms which are distinctly edible, as in examples Plate 10 and Plate 16. It is to the volva or cup, then, that we must devote our special attention as the only safe and constant character. And this leads me to the prominent and necessary consideration of another common species of Amanita, mentioned above, in which even this cup is more or less obscure.
Plate III. - Development Of Amanita Vernus
Scales and scurfy spots