The plants belonging to this family are almost exclusively herbaceous, with scattered, exstipulate leaves. The flowers are eucyclic di- or tetramerous, with the calyx and corolla deciduous, hypogynous, ☿, regular, the gynœceum with 2–several carpels (generally 2, transversely placed) (Figs. [391], [392], [393], [397]). The ovary is unilocular with parietal placentæ, but in Cruciferæ and a few others it becomes bilocular by the development of a false, membranous wall between the placentæ. The stigmas in the majority of cases are commissural, i.e. they stand above the placentæ, and not above the dorsal line of the carpels. The fruit is nearly always a capsule, which opens by the middle portions of the carpels detaching themselves as valves, bearing no seed, whilst the placentæ persist as the seed-bearing frame. Endosperm is found in Papaveraceæ and Fumariaceæ, but is absent in Cruciferæ and Capparidaceæ.—This family through the Papaveraceæ is related to the Polycarpicæ (the Nymphæaceæ), through the Capparidaceæ to the Resedaceæ in the next family.
Exceptions to the above are: Eschscholtzia, Subularia (Fig. [403]) and a few Capparidaceæ, in which perigynous flowers are found. A few Papaveraceæ and Fumariaceæ have trimerous flowers. In Fumaria and certain Cruciferæ, the fruit is a nut. The Fumariaceæ have zygomorphic flowers. Trees and shrubs are almost entirely confined to the Capparidaceæ, in which order stipules also are found.
Order 1. Papaveraceæ (Poppies). Herbaceous plants with stiff hairs and latex; flowers regular (Fig. [391]) with generally 2 (-3) sepals (which fall off as the flower opens), 2 + 2 petals (imbricate and crumpled in the bud) without spur, numerous stamens in several alternating whorls (generally a multiple of 2); carpels 2–several, united into a unilocular gynœceum. Trimerous flowers also occur. Capsule with very numerous seeds on the parietal placentæ; embryo small, with large, oleaginous endosperm (Fig. [392]).—The leaves have no stipules and are generally pinnately lobed.
Fig. 391.—A Diagram of the flower of Glaucium and the dichasium (which becomes transformed into a scorpioid cyme). B Papaver argemone, transverse section of the ovary with indication of the position of the stigmas.
Fig. 392.—Papaver somniferum: A capsule; st the stigma; v valves; h pores; B seed in longitudinal section; alb endosperm; emb embryo.
Papaver (Poppy) has large, solitary, terminal flowers; petals firmly and irregularly folded in æstivation; gynœceum formed by many (4–15) carpels; stigmas velvety, sessile and stellate (the rays stand above the placentæ) (Fig. [391] B). The edges of the carpels project deeply into the ovary, but do not meet in the centre, so that it remains unilocular. The capsule opens by pores placed close beneath the stigma, and formed of small valves alternating with the placentæ and the rays of the stigma (Fig. [391]). P. dubium, P. argemone, P. rhœas.—Chelidonium (Greater Celandine) has yellow latex, flowers in umbellate cymes (the terminal, central flower opening first) and only 2 carpels; the fruit resembles the siliqua of the Cruciferæ in having two barren valves, which are detached from the base upwards, and a seed-bearing frame, but there is no partition wall formed between the placentæ. Ch. majus.—The majority of the other genera have, like Chelidonium, 2 carpels (lateral and alternating with the sepals: Fig. [391] A) and siliqua-like fruit, thus: Eschscholtzia (perigynous) with a linear, stigma-bearing prolongation extending as far above the placentæ as above the dorsal suture of the carpels; Glaucium (Horn-Poppy); G. luteum, whose extremely long, thin capsule differs from that of Chelidonium by the formation, during ripening, of a thick, spongy (false) replum, which persists when the valves are detached; Sanguinaria with red latex, the 2 petals divided into 8–12 small petals (perhaps by dédoublement); Macleya and Bocconia (1-seeded capsule) with 2 sepals and no petals.—Trimerous flowers are found in Argemone and Platystemon (with a curious fruit, carpels free, and transversely divided and constricted into joints which separate as nut-like portions).—Meconopsis.—Hypecoum (Fig. [393] C) has tri-lobed and three cleft petals, 4 free stamens with 4-locular anthers and a jointed siliqua; it presents a transitional form to the Fumariaceæ, with which order it is sometimes included.
Pollination. Papaver and Chelidonium have no honey, and are without doubt only visited by insects for the sake of the pollen. The anthers and stigmas mature about the same time.—There are 80 species; especially from warm climates. Officinal: Papaver somniferum (Opium-Poppy); the latex of its unripe capsules is obtained by incisions, and dried (opium); it contains many alkaloids: morphine, papaverine, narcotine, thebaine, etc. The oleaginous seeds are also used in the manufacture of oil. Its home is in the East, where it is extensively cultivated. The petals of the Corn-poppy (P. rhœas) are also officinal. Several species are cultivated as ornamental plants.
Order 2. Fumariacæ (Fumitories). This order differs from the closely allied Papaveraceæ in the absence of latex, a poorer flower, generally transversely zygomorphic (Fig. [393] B), in which case one or both of the outer lateral petals are gibbous, or prolonged into a spur; the stamens are especially anomalous. Sepals 2, caducous; petals 2 + 2; stamens 2, tripartite; each lateral anther is bilocular (Figs. [393] A, B; 395); gynœceum bicarpellate. The fruit is a nut or siliqua-like capsule. Endosperm.—Herbs with scattered, repeatedly pinnately-divided leaves without stipules, generally quite glabrous and glaucous; the flowers are arranged in racemes with subtending bracts, but the bracteoles are sometimes suppressed.