Family 34. Dipsacales.
The leaves are opposite and without stipules. The flower (Figs. [593], [595], [598], [599], [600]) is epigynous, zygomorphic or asymmetrical, 5-merous with S5, P5, stamens typically 5, but by suppression never more than 4, sometimes less, carpels 3–2. The calyx is more or less insignificant, and almost suppressed in the extreme forms. The ovary has 3–1 loculi, but only one loculus has an ovule, which is pendulous with the micropyle turned upwards (Fig. [594]). Fruit a nut. Embryo straight, with the radicle pointing upwards (Fig. [597]), without or with endosperm.
The inflorescences are distinct dichasia in Valerianaceæ, but in Dipsacaceæ and Calyceraceæ they are crowded together into capitula.
This family is closely allied to the Rubiales through the Valerianaceæ, which have almost the same structure as many of the Caprifoliaceæ. It attains the highest development in the Dipsacaceæ, which are composite plants, but differs from Compositæ in the position of the ovule, etc.
Order 1. Valerianaceæ. Herbaceous plants or under-shrubs with opposite leaves, often pinnate; stipules absent. The flowers are borne in dichasia and in scorpioid cymose inflorescences and are entirely without any plane of symmetry (Fig. [593]). The calyx and corolla are 5-merous, but the calyx is frequently very insignificant and ultimately a pappus, as in Compositæ; the corolla is frequently saccate or produced into a spur at the base. Most frequently, only 3 (4–1) of the 5 stamens are developed; these are free. Carpels 3, which form an inferior ovary, often with 3 loculi, but only 1 of the loculi contains 1 pendulous, anatropous ovule (Figs. [593], [594] A), the other loculi are empty and shrink up more or less completely. (Compare Fig. [593] A, B). Style 1, stigma tripartite. Endosperm absent; embryo straight, with the radicle directed upwards.
The inflorescences are dichasia, or unipared scorpioid cymes with the branches developed in the axil of the second bracteole. Both the bracteoles are generally present and frequently form 4 very regular, longitudinal rows on the branches of the inflorescence.—5 stamens do not occur (except perhaps in Patrinia). The suppression of stamens and carpels takes place most readily on the anterior side of the flower and that turned towards the first bracteole (a) (Fig. [593]), whose branch is suppressed in the dichasium; after this the posterior median stamen is next suppressed.
By the vegetative characters as well as by the inflorescence and the flower, the order is allied to the Caprifoliaceæ and especially to the Sambuceæ.
Fig. 593.—A Diagram of Valeriana officinalis. B Diagram of Centranthus.
In the least modified (oldest) forms, Patrinia and Nardostachys, there is an almost regular flower, a 5-merous calyx, 4 stamens, and 3 loculi in the ovary, 2 of which however are barren. The stamens in Valerianella are reduced to 3, in Fedia to 2 (posterior), and the calyx is less distinctly 5-dentate; the 2 empty loculi in the ovary are still visible. Fedia has a small spur at the base of the corolla. Valeriana has a very reduced, hair-like calyx (pappus), an unsymmetrical, salver-shaped corolla with a sac-like, nectariferous spur at the base, 3 stamens and only 1 loculus in the ovary (Figs. [594], [593]). Centranthus (Fig. [593]) is still further reduced. The corolla has a spur and only 1 stamen; unipared scorpioid cymes with 4 rows of bracteoles. In the last two genera there is a peculiar wall in the corolla-tube, which divides it longitudinally into two compartments (indicated by a dotted line in Fig. [593]), one of which encloses the style. This wall is low in Valeriana, but in Centranthus it reaches as far as the throat.—The rays of the pappus are pinnately branched and rolled up before the ripening of the fruit. 12–20 in number (Fig. [594] A, B).