There are many different kinds of Poppy; but they all agree in the corolla of their flowers being in four petals, or in some number divisible by four; and in the calyx, which is generally in two sepals, dropping off as soon as the flowers expand. All the species abound in a milky juice, which poisons by stupifying; and they all agree in the general construction of the capsule, with its fleshy envelop and its stigma-formed lid. The petals are always crumpled in the bud, and they fall very soon, so that the beauty of the flowers is very short-lived. The flower-buds droop; but when the flowers expand, the stalk becomes erect, and remains so while the capsule containing the seeds is ripening; a wise provision, common to many plants, to prevent the seeds from falling too soon. The calyx of most of the Poppies is in only two sepals; but in the two showy perennial species, called _P. orientale_ and _P. bracteatum_, the calyx is in three sepals. Among the other plants belonging to the order Papaveraceæ, may be mentioned the Horned Poppy (_Glaucium luteum_), which, instead of an obovate capsule, has a long horn-like pod, divided into two cells, the valves opening from the top to the bottom. The whole plant is glaucous; and the leaves, which are broad and notched, clasp the stem at their base, like those of the Opium Poppy. The Prickly Poppy (_Argemone mexicana_) has the whole plant covered with strong prickles; the leaves are wrinkled and curved up at the margin; the calyx has three sepals; and the capsules are in four or five valves, the stigmas forming a kind of cross at the top. The stem and leaves when bruised give out a thick glutinous juice, which, instead of being white like that of the Poppy, is yellow.